From 1a2383e8b84c0451fd9b1eec3b9aab16f30b597c Mon Sep 17 00:00:00 2001 From: Tiezhu Yang Date: Wed, 23 Mar 2022 16:06:51 -0700 Subject: panic: unset panic_on_warn inside panic() In the current code, the following three places need to unset panic_on_warn before calling panic() to avoid recursive panics: kernel/kcsan/report.c: print_report() kernel/sched/core.c: __schedule_bug() mm/kfence/report.c: kfence_report_error() In order to avoid copy-pasting "panic_on_warn = 0" all over the places, it is better to move it inside panic() and then remove it from the other places. Link: https://lkml.kernel.org/r/1644324666-15947-4-git-send-email-yangtiezhu@loongson.cn Signed-off-by: Tiezhu Yang Reviewed-by: Marco Elver Cc: Andrey Ryabinin Cc: Baoquan He Cc: Jonathan Corbet Cc: Xuefeng Li Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/panic.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) (limited to 'kernel/panic.c') diff --git a/kernel/panic.c b/kernel/panic.c index 55b50e052ec3..95ba825522dd 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -185,6 +185,16 @@ void panic(const char *fmt, ...) int old_cpu, this_cpu; bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers; + if (panic_on_warn) { + /* + * This thread may hit another WARN() in the panic path. + * Resetting this prevents additional WARN() from panicking the + * system on this thread. Other threads are blocked by the + * panic_mutex in panic(). + */ + panic_on_warn = 0; + } + /* * Disable local interrupts. This will prevent panic_smp_self_stop * from deadlocking the first cpu that invokes the panic, since @@ -576,16 +586,8 @@ void __warn(const char *file, int line, void *caller, unsigned taint, if (regs) show_regs(regs); - if (panic_on_warn) { - /* - * This thread may hit another WARN() in the panic path. - * Resetting this prevents additional WARN() from panicking the - * system on this thread. Other threads are blocked by the - * panic_mutex in panic(). - */ - panic_on_warn = 0; + if (panic_on_warn) panic("panic_on_warn set ...\n"); - } if (!regs) dump_stack(); -- cgit v1.2.3 From 8d470a45d1a65e6a308aeee5da7f5b37d3303c04 Mon Sep 17 00:00:00 2001 From: "Guilherme G. Piccoli" Date: Wed, 23 Mar 2022 16:07:06 -0700 Subject: panic: add option to dump all CPUs backtraces in panic_print Currently the "panic_print" parameter/sysctl allows some interesting debug information to be printed during a panic event. This is useful for example in cases the user cannot kdump due to resource limits, or if the user collects panic logs in a serial output (or pstore) and prefers a fast reboot instead of a kdump. Happens that currently there's no way to see all CPUs backtraces in a panic using "panic_print" on architectures that support that. We do have "oops_all_cpu_backtrace" sysctl, but although partially overlapping in the functionality, they are orthogonal in nature: "panic_print" is a panic tuning (and we have panics without oopses, like direct calls to panic() or maybe other paths that don't go through oops_enter() function), and the original purpose of "oops_all_cpu_backtrace" is to provide more information on oopses for cases in which the users desire to continue running the kernel even after an oops, i.e., used in non-panic scenarios. So, we hereby introduce an additional bit for "panic_print" to allow dumping the CPUs backtraces during a panic event. Link: https://lkml.kernel.org/r/20211109202848.610874-3-gpiccoli@igalia.com Signed-off-by: Guilherme G. Piccoli Reviewed-by: Feng Tang Cc: Iurii Zaikin Cc: Kees Cook Cc: Luis Chamberlain Cc: Samuel Iglesias Gonsalvez Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/admin-guide/kernel-parameters.txt | 1 + Documentation/admin-guide/sysctl/kernel.rst | 1 + kernel/panic.c | 4 ++++ 3 files changed, 6 insertions(+) (limited to 'kernel/panic.c') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7123524a86b8..6287f6be4a98 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3726,6 +3726,7 @@ bit 3: print locks info if CONFIG_LOCKDEP is on bit 4: print ftrace buffer bit 5: print all printk messages in buffer + bit 6: print all CPUs backtrace (if available in the arch) panic_on_taint= Bitmask for conditionally calling panic() in add_taint() Format: [,nousertaint] diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index 0f86e9f93129..cfd6c20ce42e 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -796,6 +796,7 @@ bit 2 print timer info bit 3 print locks info if ``CONFIG_LOCKDEP`` is on bit 4 print ftrace buffer bit 5 print all printk messages in buffer +bit 6 print all CPUs backtrace (if available in the arch) ===== ============================================ So for example to print tasks and memory info on panic, user can:: diff --git a/kernel/panic.c b/kernel/panic.c index 95ba825522dd..3c3fb36d8d41 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -66,6 +66,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); #define PANIC_PRINT_LOCK_INFO 0x00000008 #define PANIC_PRINT_FTRACE_INFO 0x00000010 #define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020 +#define PANIC_PRINT_ALL_CPU_BT 0x00000040 unsigned long panic_print; ATOMIC_NOTIFIER_HEAD(panic_notifier_list); @@ -152,6 +153,9 @@ static void panic_print_sys_info(void) if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) console_flush_on_panic(CONSOLE_REPLAY_ALL); + if (panic_print & PANIC_PRINT_ALL_CPU_BT) + trigger_all_cpu_backtrace(); + if (panic_print & PANIC_PRINT_TASK_INFO) show_state(); -- cgit v1.2.3 From f953f140f318a641c443b0b8c618155ed90a7a10 Mon Sep 17 00:00:00 2001 From: "Guilherme G. Piccoli" Date: Wed, 23 Mar 2022 16:07:09 -0700 Subject: panic: move panic_print before kmsg dumpers The panic_print setting allows users to collect more information in a panic event, like memory stats, tasks, CPUs backtraces, etc. This is an interesting debug mechanism, but currently the print event happens *after* kmsg_dump(), meaning that pstore, for example, cannot collect a dmesg with the panic_print extra information. This patch changes that in 2 steps: (a) The panic_print setting allows to replay the existing kernel log buffer to the console (bit 5), besides the extra information dump. This functionality makes sense only at the end of the panic() function. So, we hereby allow to distinguish the two situations by a new boolean parameter in the function panic_print_sys_info(). (b) With the above change, we can safely call panic_print_sys_info() before kmsg_dump(), allowing to dump the extra information when using pstore or other kmsg dumpers. The additional messages from panic_print could overwrite the oldest messages when the buffer is full. The only reasonable solution is to use a large enough log buffer, hence we added an advice into the kernel parameters documentation about that. Link: https://lkml.kernel.org/r/20220214141308.841525-1-gpiccoli@igalia.com Signed-off-by: Guilherme G. Piccoli Acked-by: Baoquan He Reviewed-by: Petr Mladek Reviewed-by: Sergey Senozhatsky Cc: Feng Tang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ kernel/panic.c | 13 +++++++++---- 2 files changed, 13 insertions(+), 4 deletions(-) (limited to 'kernel/panic.c') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6287f6be4a98..a18e30a95931 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3727,6 +3727,10 @@ bit 4: print ftrace buffer bit 5: print all printk messages in buffer bit 6: print all CPUs backtrace (if available in the arch) + *Be aware* that this option may print a _lot_ of lines, + so there are risks of losing older messages in the log. + Use this option carefully, maybe worth to setup a + bigger log buffer with "log_buf_len" along with this. panic_on_taint= Bitmask for conditionally calling panic() in add_taint() Format: [,nousertaint] diff --git a/kernel/panic.c b/kernel/panic.c index 3c3fb36d8d41..eb4dfb932c85 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -148,10 +148,13 @@ void nmi_panic(struct pt_regs *regs, const char *msg) } EXPORT_SYMBOL(nmi_panic); -static void panic_print_sys_info(void) +static void panic_print_sys_info(bool console_flush) { - if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) - console_flush_on_panic(CONSOLE_REPLAY_ALL); + if (console_flush) { + if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) + console_flush_on_panic(CONSOLE_REPLAY_ALL); + return; + } if (panic_print & PANIC_PRINT_ALL_CPU_BT) trigger_all_cpu_backtrace(); @@ -286,6 +289,8 @@ void panic(const char *fmt, ...) */ atomic_notifier_call_chain(&panic_notifier_list, 0, buf); + panic_print_sys_info(false); + kmsg_dump(KMSG_DUMP_PANIC); /* @@ -316,7 +321,7 @@ void panic(const char *fmt, ...) debug_locks_off(); console_flush_on_panic(CONSOLE_FLUSH_PENDING); - panic_print_sys_info(); + panic_print_sys_info(true); if (!panic_blink) panic_blink = no_blink; -- cgit v1.2.3 From 9df918698408fd914493aba0b7858fef50eba63a Mon Sep 17 00:00:00 2001 From: tangmeng Date: Fri, 18 Feb 2022 18:59:12 +0800 Subject: kernel/panic: move panic sysctls to its own file kernel/sysctl.c is a kitchen sink where everyone leaves their dirty dishes, this makes it very difficult to maintain. To help with this maintenance let's start by moving sysctls to places where they actually belong. The proc sysctl maintainers do not want to know what sysctl knobs you wish to add for your own piece of code, we just care about the core logic. All filesystem syctls now get reviewed by fs folks. This commit follows the commit of fs, move the oops_all_cpu_backtrace sysctl to its own file, kernel/panic.c. Signed-off-by: tangmeng Signed-off-by: Luis Chamberlain --- include/linux/panic.h | 6 ------ kernel/panic.c | 26 +++++++++++++++++++++++++- kernel/sysctl.c | 11 ----------- 3 files changed, 25 insertions(+), 18 deletions(-) (limited to 'kernel/panic.c') diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..e71161da69c4 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -15,12 +15,6 @@ extern void oops_enter(void); extern void oops_exit(void); extern bool oops_may_print(void); -#ifdef CONFIG_SMP -extern unsigned int sysctl_oops_all_cpu_backtrace; -#else -#define sysctl_oops_all_cpu_backtrace 0 -#endif /* CONFIG_SMP */ - extern int panic_timeout; extern unsigned long panic_print; extern int panic_on_oops; diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..eb3f2fe4f6d7 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -43,7 +43,9 @@ * Should we dump all CPUs backtraces in an oops event? * Defaults to 0, can be changed via sysctl. */ -unsigned int __read_mostly sysctl_oops_all_cpu_backtrace; +static unsigned int __read_mostly sysctl_oops_all_cpu_backtrace; +#else +#define sysctl_oops_all_cpu_backtrace 0 #endif /* CONFIG_SMP */ int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE; @@ -73,6 +75,28 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list); EXPORT_SYMBOL(panic_notifier_list); +#if defined(CONFIG_SMP) && defined(CONFIG_SYSCTL) +static struct ctl_table kern_panic_table[] = { + { + .procname = "oops_all_cpu_backtrace", + .data = &sysctl_oops_all_cpu_backtrace, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + +static __init int kernel_panic_sysctls_init(void) +{ + register_sysctl_init("kernel", kern_panic_table); + return 0; +} +late_initcall(kernel_panic_sysctls_init); +#endif + static long no_blink(int state) { return 0; diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 95380d250c8c..90fc2212b536 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1922,17 +1922,6 @@ static struct ctl_table kern_table[] = { .proc_handler = proc_dointvec, }, #endif -#ifdef CONFIG_SMP - { - .procname = "oops_all_cpu_backtrace", - .data = &sysctl_oops_all_cpu_backtrace, - .maxlen = sizeof(int), - .mode = 0644, - .proc_handler = proc_dointvec_minmax, - .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_ONE, - }, -#endif /* CONFIG_SMP */ { .procname = "pid_max", .data = &pid_max, -- cgit v1.2.3 From 2bb2b7b57f81255c13f4395ea911d6bdc70c9fe2 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 21 Apr 2022 23:28:47 +0206 Subject: printk: add functions to prefer direct printing Once kthread printing is available, console printing will no longer occur in the context of the printk caller. However, there are some special contexts where it is desirable for the printk caller to directly print out kernel messages. Using pr_flush() to wait for threaded printers is only possible if the caller is in a sleepable context and the kthreads are active. That is not always the case. Introduce printk_prefer_direct_enter() and printk_prefer_direct_exit() functions to explicitly (and globally) activate/deactivate preferred direct console printing. The term "direct console printing" refers to printing to all enabled consoles from the context of the printk caller. The term "prefer" is used because this type of printing is only best effort. If the console is currently locked or other printers are already actively printing, the printk caller will need to rely on the other contexts to handle the printing. This preferred direct printing is how all printing has been handled until now (unless it was explicitly deferred). When kthread printing is introduced, there may be some unanticipated problems due to kthreads being unable to flush important messages. In order to minimize such risks, preferred direct printing is activated for the primary important messages when the system experiences general types of major errors. These are: - emergency reboot/shutdown - cpu and rcu stalls - hard and soft lockups - hung tasks - warn - sysrq Note that since kthread printing does not yet exist, no behavior changes result from this commit. This is only implementing the counter and marking the various places where preferred direct printing is active. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Acked-by: Paul E. McKenney # for RCU Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220421212250.565456-13-john.ogness@linutronix.de --- drivers/tty/sysrq.c | 2 ++ include/linux/printk.h | 11 +++++++++++ kernel/hung_task.c | 11 ++++++++++- kernel/panic.c | 4 ++++ kernel/printk/printk.c | 28 ++++++++++++++++++++++++++++ kernel/rcu/tree_stall.h | 2 ++ kernel/reboot.c | 14 +++++++++++++- kernel/watchdog.c | 4 ++++ kernel/watchdog_hld.c | 4 ++++ 9 files changed, 78 insertions(+), 2 deletions(-) (limited to 'kernel/panic.c') diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index bbfd004449b5..2884cd638d64 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -578,6 +578,7 @@ void __handle_sysrq(int key, bool check_mask) rcu_sysrq_start(); rcu_read_lock(); + printk_prefer_direct_enter(); /* * Raise the apparent loglevel to maximum so that the sysrq header * is shown to provide the user with positive feedback. We do not @@ -619,6 +620,7 @@ void __handle_sysrq(int key, bool check_mask) pr_cont("\n"); console_loglevel = orig_log_level; } + printk_prefer_direct_exit(); rcu_read_unlock(); rcu_sysrq_end(); diff --git a/include/linux/printk.h b/include/linux/printk.h index 091fba7283e1..cd26aab0ab2a 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -170,6 +170,9 @@ extern void __printk_safe_exit(void); #define printk_deferred_enter __printk_safe_enter #define printk_deferred_exit __printk_safe_exit +extern void printk_prefer_direct_enter(void); +extern void printk_prefer_direct_exit(void); + extern bool pr_flush(int timeout_ms, bool reset_on_progress); /* @@ -222,6 +225,14 @@ static inline void printk_deferred_exit(void) { } +static inline void printk_prefer_direct_enter(void) +{ +} + +static inline void printk_prefer_direct_exit(void) +{ +} + static inline bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 52501e5f7655..02a65d554340 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -127,6 +127,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) * complain: */ if (sysctl_hung_task_warnings) { + printk_prefer_direct_enter(); + if (sysctl_hung_task_warnings > 0) sysctl_hung_task_warnings--; pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", @@ -142,6 +144,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) if (sysctl_hung_task_all_cpu_backtrace) hung_task_show_all_bt = true; + + printk_prefer_direct_exit(); } touch_nmi_watchdog(); @@ -204,12 +208,17 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) } unlock: rcu_read_unlock(); - if (hung_task_show_lock) + if (hung_task_show_lock) { + printk_prefer_direct_enter(); debug_show_all_locks(); + printk_prefer_direct_exit(); + } if (hung_task_show_all_bt) { hung_task_show_all_bt = false; + printk_prefer_direct_enter(); trigger_all_cpu_backtrace(); + printk_prefer_direct_exit(); } if (hung_task_call_panic) diff --git a/kernel/panic.c b/kernel/panic.c index 55b50e052ec3..7d422597403f 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -560,6 +560,8 @@ void __warn(const char *file, int line, void *caller, unsigned taint, { disable_trace_on_warning(); + printk_prefer_direct_enter(); + if (file) pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n", raw_smp_processor_id(), current->pid, file, line, @@ -597,6 +599,8 @@ void __warn(const char *file, int line, void *caller, unsigned taint, /* Just a warning, don't kill lockdep. */ add_taint(taint, LOCKDEP_STILL_OK); + + printk_prefer_direct_exit(); } #ifndef __WARN_FLAGS diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index a06999d55278..ed7f738261cc 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -362,6 +362,34 @@ static int console_msg_format = MSG_FORMAT_DEFAULT; static DEFINE_MUTEX(syslog_lock); #ifdef CONFIG_PRINTK +static atomic_t printk_prefer_direct = ATOMIC_INIT(0); + +/** + * printk_prefer_direct_enter - cause printk() calls to attempt direct + * printing to all enabled consoles + * + * Since it is not possible to call into the console printing code from any + * context, there is no guarantee that direct printing will occur. + * + * This globally effects all printk() callers. + * + * Context: Any context. + */ +void printk_prefer_direct_enter(void) +{ + atomic_inc(&printk_prefer_direct); +} + +/** + * printk_prefer_direct_exit - restore printk() behavior + * + * Context: Any context. + */ +void printk_prefer_direct_exit(void) +{ + WARN_ON(atomic_dec_if_positive(&printk_prefer_direct) < 0); +} + DECLARE_WAIT_QUEUE_HEAD(log_wait); /* All 3 protected by @syslog_lock. */ /* the next printk record to read by syslog(READ) or /proc/kmsg */ diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 0c5d8516516a..d612707c2ed0 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -619,6 +619,7 @@ static void print_cpu_stall(unsigned long gps) * See Documentation/RCU/stallwarn.rst for info on how to debug * RCU CPU stall warnings. */ + printk_prefer_direct_enter(); trace_rcu_stall_warning(rcu_state.name, TPS("SelfDetected")); pr_err("INFO: %s self-detected stall on CPU\n", rcu_state.name); raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags); @@ -656,6 +657,7 @@ static void print_cpu_stall(unsigned long gps) */ set_tsk_need_resched(current); set_preempt_need_resched(); + printk_prefer_direct_exit(); } static void check_cpu_stall(struct rcu_data *rdp) diff --git a/kernel/reboot.c b/kernel/reboot.c index 6bcc5d6a6572..4177645e74d6 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -447,9 +447,11 @@ static int __orderly_reboot(void) ret = run_cmd(reboot_cmd); if (ret) { + printk_prefer_direct_enter(); pr_warn("Failed to start orderly reboot: forcing the issue\n"); emergency_sync(); kernel_restart(NULL); + printk_prefer_direct_exit(); } return ret; @@ -462,6 +464,7 @@ static int __orderly_poweroff(bool force) ret = run_cmd(poweroff_cmd); if (ret && force) { + printk_prefer_direct_enter(); pr_warn("Failed to start orderly shutdown: forcing the issue\n"); /* @@ -471,6 +474,7 @@ static int __orderly_poweroff(bool force) */ emergency_sync(); kernel_power_off(); + printk_prefer_direct_exit(); } return ret; @@ -528,6 +532,8 @@ EXPORT_SYMBOL_GPL(orderly_reboot); */ static void hw_failure_emergency_poweroff_func(struct work_struct *work) { + printk_prefer_direct_enter(); + /* * We have reached here after the emergency shutdown waiting period has * expired. This means orderly_poweroff has not been able to shut off @@ -544,6 +550,8 @@ static void hw_failure_emergency_poweroff_func(struct work_struct *work) */ pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n"); emergency_restart(); + + printk_prefer_direct_exit(); } static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work, @@ -582,11 +590,13 @@ void hw_protection_shutdown(const char *reason, int ms_until_forced) { static atomic_t allow_proceed = ATOMIC_INIT(1); + printk_prefer_direct_enter(); + pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason); /* Shutdown should be initiated only once. */ if (!atomic_dec_and_test(&allow_proceed)) - return; + goto out; /* * Queue a backup emergency shutdown in the event of @@ -594,6 +604,8 @@ void hw_protection_shutdown(const char *reason, int ms_until_forced) */ hw_failure_emergency_poweroff(ms_until_forced); orderly_poweroff(true); +out: + printk_prefer_direct_exit(); } EXPORT_SYMBOL_GPL(hw_protection_shutdown); diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 9166220457bc..40024e03d422 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -424,6 +424,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) /* Start period for the next softlockup warning. */ update_report_ts(); + printk_prefer_direct_enter(); + pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); @@ -442,6 +444,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); if (softlockup_panic) panic("softlockup: hung tasks"); + + printk_prefer_direct_exit(); } return HRTIMER_RESTART; diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c index 247bf0b1582c..701f35f0e2d4 100644 --- a/kernel/watchdog_hld.c +++ b/kernel/watchdog_hld.c @@ -135,6 +135,8 @@ static void watchdog_overflow_callback(struct perf_event *event, if (__this_cpu_read(hard_watchdog_warn) == true) return; + printk_prefer_direct_enter(); + pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", this_cpu); print_modules(); @@ -155,6 +157,8 @@ static void watchdog_overflow_callback(struct perf_event *event, if (hardlockup_panic) nmi_panic(regs, "Hard LOCKUP"); + printk_prefer_direct_exit(); + __this_cpu_write(hard_watchdog_warn, true); return; } -- cgit v1.2.3 From 595b893e2087de306d0781795fb8ec47873596a6 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 3 May 2022 13:55:00 -0700 Subject: randstruct: Reorganize Kconfigs and attribute macros In preparation for Clang supporting randstruct, reorganize the Kconfigs, move the attribute macros, and generalize the feature to be named CONFIG_RANDSTRUCT for on/off, CONFIG_RANDSTRUCT_FULL for the full randomization mode, and CONFIG_RANDSTRUCT_PERFORMANCE for the cache-line sized mode. Cc: linux-hardening@vger.kernel.org Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220503205503.3054173-4-keescook@chromium.org --- Documentation/kbuild/reproducible-builds.rst | 7 ++-- arch/riscv/Kconfig | 2 +- arch/x86/mm/pti.c | 2 +- include/linux/compiler-gcc.h | 8 ---- include/linux/compiler_types.h | 14 +++---- include/linux/vermagic.h | 8 ++-- kernel/panic.c | 2 +- scripts/Makefile.gcc-plugins | 4 +- scripts/gcc-plugins/Kconfig | 38 ----------------- security/Kconfig.hardening | 62 ++++++++++++++++++++++++++++ 10 files changed, 81 insertions(+), 66 deletions(-) (limited to 'kernel/panic.c') diff --git a/Documentation/kbuild/reproducible-builds.rst b/Documentation/kbuild/reproducible-builds.rst index 3b25655e441b..81ff30505d35 100644 --- a/Documentation/kbuild/reproducible-builds.rst +++ b/Documentation/kbuild/reproducible-builds.rst @@ -99,10 +99,9 @@ unreproducible parts can be treated as sources: Structure randomisation ----------------------- -If you enable ``CONFIG_GCC_PLUGIN_RANDSTRUCT``, you will need to -pre-generate the random seed in -``scripts/gcc-plugins/randomize_layout_seed.h`` so the same value -is used in rebuilds. +If you enable ``CONFIG_RANDSTRUCT``, you will need to pre-generate +the random seed in ``scripts/gcc-plugins/randomize_layout_seed.h`` +so the same value is used in rebuilds. Debug info conflicts -------------------- diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 00fd9c548f26..3ac2a81a55eb 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -468,7 +468,7 @@ config CC_HAVE_STACKPROTECTOR_TLS config STACKPROTECTOR_PER_TASK def_bool y - depends on !GCC_PLUGIN_RANDSTRUCT + depends on !RANDSTRUCT depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS config PHYS_RAM_BASE_FIXED diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 5d5c7bb50ce9..ffe3b3a087fe 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -540,7 +540,7 @@ static inline bool pti_kernel_image_global_ok(void) * cases where RANDSTRUCT is in use to help keep the layout a * secret. */ - if (IS_ENABLED(CONFIG_GCC_PLUGIN_RANDSTRUCT)) + if (IS_ENABLED(CONFIG_RANDSTRUCT)) return false; return true; diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 52299c957c98..a0c55eeaeaf1 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -66,14 +66,6 @@ __builtin_unreachable(); \ } while (0) -#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__) -#define __randomize_layout __attribute__((randomize_layout)) -#define __no_randomize_layout __attribute__((no_randomize_layout)) -/* This anon struct can add padding, so only enable it under randstruct. */ -#define randomized_struct_fields_start struct { -#define randomized_struct_fields_end } __randomize_layout; -#endif - /* * GCC 'asm goto' miscompiles certain code sequences: * diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 1c2c33ae1b37..d08dfcb0ac68 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -242,15 +242,15 @@ struct ftrace_likely_data { # define __latent_entropy #endif -#ifndef __randomize_layout +#if defined(RANDSTRUCT) && !defined(__CHECKER__) +# define __randomize_layout __designated_init __attribute__((randomize_layout)) +# define __no_randomize_layout __attribute__((no_randomize_layout)) +/* This anon struct can add padding, so only enable it under randstruct. */ +# define randomized_struct_fields_start struct { +# define randomized_struct_fields_end } __randomize_layout; +#else # define __randomize_layout __designated_init -#endif - -#ifndef __no_randomize_layout # define __no_randomize_layout -#endif - -#ifndef randomized_struct_fields_start # define randomized_struct_fields_start # define randomized_struct_fields_end #endif diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h index 329d63babaeb..efb51a2da599 100644 --- a/include/linux/vermagic.h +++ b/include/linux/vermagic.h @@ -32,11 +32,11 @@ #else #define MODULE_VERMAGIC_MODVERSIONS "" #endif -#ifdef RANDSTRUCT_PLUGIN +#ifdef RANDSTRUCT #include -#define MODULE_RANDSTRUCT_PLUGIN "RANDSTRUCT_PLUGIN_" RANDSTRUCT_HASHED_SEED +#define MODULE_RANDSTRUCT "RANDSTRUCT_" RANDSTRUCT_HASHED_SEED #else -#define MODULE_RANDSTRUCT_PLUGIN +#define MODULE_RANDSTRUCT #endif #define VERMAGIC_STRING \ @@ -44,6 +44,6 @@ MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT \ MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS \ MODULE_ARCH_VERMAGIC \ - MODULE_RANDSTRUCT_PLUGIN + MODULE_RANDSTRUCT #endif /* _LINUX_VERMAGIC_H */ diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..8355b19676f8 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -48,7 +48,7 @@ unsigned int __read_mostly sysctl_oops_all_cpu_backtrace; int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE; static unsigned long tainted_mask = - IS_ENABLED(CONFIG_GCC_PLUGIN_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0; + IS_ENABLED(CONFIG_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0; static int pause_on_oops; static int pause_on_oops_flag; static DEFINE_SPINLOCK(pause_on_oops_lock); diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 927c3dd57f84..827c47ce5c73 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -24,8 +24,8 @@ gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) \ gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) += randomize_layout_plugin.so gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) \ - += -DRANDSTRUCT_PLUGIN -gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE) \ + += -DRANDSTRUCT +gcc-plugin-cflags-$(CONFIG_RANDSTRUCT_PERFORMANCE) \ += -fplugin-arg-randomize_layout_plugin-performance-mode gcc-plugin-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak_plugin.so diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig index 51d81c3f03d6..e383cda05367 100644 --- a/scripts/gcc-plugins/Kconfig +++ b/scripts/gcc-plugins/Kconfig @@ -46,44 +46,6 @@ config GCC_PLUGIN_LATENT_ENTROPY * https://grsecurity.net/ * https://pax.grsecurity.net/ -config GCC_PLUGIN_RANDSTRUCT - bool "Randomize layout of sensitive kernel structures" - select MODVERSIONS if MODULES - help - If you say Y here, the layouts of structures that are entirely - function pointers (and have not been manually annotated with - __no_randomize_layout), or structures that have been explicitly - marked with __randomize_layout, will be randomized at compile-time. - This can introduce the requirement of an additional information - exposure vulnerability for exploits targeting these structure - types. - - Enabling this feature will introduce some performance impact, - slightly increase memory usage, and prevent the use of forensic - tools like Volatility against the system (unless the kernel - source tree isn't cleaned after kernel installation). - - The seed used for compilation is located at - scripts/gcc-plugins/randomize_layout_seed.h. It remains after - a make clean to allow for external modules to be compiled with - the existing seed and will be removed by a make mrproper or - make distclean. - - This plugin was ported from grsecurity/PaX. More information at: - * https://grsecurity.net/ - * https://pax.grsecurity.net/ - -config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE - bool "Use cacheline-aware structure randomization" - depends on GCC_PLUGIN_RANDSTRUCT - depends on !COMPILE_TEST # do not reduce test coverage - help - If you say Y here, the RANDSTRUCT randomization will make a - best effort at restricting randomization to cacheline-sized - groups of elements. It will further not randomize bitfields - in structures. This reduces the performance hit of RANDSTRUCT - at the cost of weakened randomization. - config GCC_PLUGIN_ARM_SSP_PER_TASK bool depends on GCC_PLUGINS && ARM diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index ded4d7c0d132..364e3f8c6eea 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -266,4 +266,66 @@ config ZERO_CALL_USED_REGS endmenu +choice + prompt "Randomize layout of sensitive kernel structures" + default RANDSTRUCT_FULL if COMPILE_TEST && GCC_PLUGINS + default RANDSTRUCT_NONE + help + If you enable this, the layouts of structures that are entirely + function pointers (and have not been manually annotated with + __no_randomize_layout), or structures that have been explicitly + marked with __randomize_layout, will be randomized at compile-time. + This can introduce the requirement of an additional information + exposure vulnerability for exploits targeting these structure + types. + + Enabling this feature will introduce some performance impact, + slightly increase memory usage, and prevent the use of forensic + tools like Volatility against the system (unless the kernel + source tree isn't cleaned after kernel installation). + + The seed used for compilation is located at + scripts/randomize_layout_seed.h. It remains after a "make clean" + to allow for external modules to be compiled with the existing + seed and will be removed by a "make mrproper" or "make distclean". + + config RANDSTRUCT_NONE + bool "Disable structure layout randomization" + help + Build normally: no structure layout randomization. + + config RANDSTRUCT_FULL + bool "Fully randomize structure layout" + depends on GCC_PLUGINS + select MODVERSIONS if MODULES + help + Fully randomize the member layout of sensitive + structures as much as possible, which may have both a + memory size and performance impact. + + config RANDSTRUCT_PERFORMANCE + bool "Limit randomization of structure layout to cache-lines" + depends on GCC_PLUGINS + select MODVERSIONS if MODULES + help + Randomization of sensitive kernel structures will make a + best effort at restricting randomization to cacheline-sized + groups of members. It will further not randomize bitfields + in structures. This reduces the performance hit of RANDSTRUCT + at the cost of weakened randomization. +endchoice + +config RANDSTRUCT + def_bool !RANDSTRUCT_NONE + +config GCC_PLUGIN_RANDSTRUCT + def_bool GCC_PLUGINS && RANDSTRUCT + help + Use GCC plugin to randomize structure layout. + + This plugin was ported from grsecurity/PaX. More + information at: + * https://grsecurity.net/ + * https://pax.grsecurity.net/ + endmenu -- cgit v1.2.3 From b87f02307d3cfbda768520f0687c51ca77e14fc3 Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Wed, 15 Jun 2022 18:28:05 +0200 Subject: printk: Wait for the global console lock when the system is going down There are reports that the console kthreads block the global console lock when the system is going down, for example, reboot, panic. First part of the solution was to block kthreads in these problematic system states so they stopped handling newly added messages. Second part of the solution is to wait when for the kthreads when they are actively printing. It solves the problem when a message was printed before the system entered the problematic state and the kthreads managed to step in. A busy waiting has to be used because panic() can be called in any context and in an unknown state of the scheduler. There must be a timeout because the kthread might get stuck or sleeping and never release the lock. The timeout 10s is an arbitrary value inspired by the softlockup timeout. Link: https://lore.kernel.org/r/20220610205038.GA3050413@paulmck-ThinkPad-P17-Gen-1 Link: https://lore.kernel.org/r/CAMdYzYpF4FNTBPZsEFeWRuEwSies36QM_As8osPWZSr2q-viEA@mail.gmail.com Signed-off-by: Petr Mladek Tested-by: Paul E. McKenney Link: https://lore.kernel.org/r/20220615162805.27962-3-pmladek@suse.com --- include/linux/printk.h | 5 +++++ kernel/panic.c | 2 ++ kernel/printk/internal.h | 2 ++ kernel/printk/printk.c | 4 ++++ kernel/printk/printk_safe.c | 32 ++++++++++++++++++++++++++++++++ kernel/reboot.c | 2 ++ 6 files changed, 47 insertions(+) (limited to 'kernel/panic.c') diff --git a/include/linux/printk.h b/include/linux/printk.h index cd26aab0ab2a..c1e07c0652c7 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -174,6 +174,7 @@ extern void printk_prefer_direct_enter(void); extern void printk_prefer_direct_exit(void); extern bool pr_flush(int timeout_ms, bool reset_on_progress); +extern void try_block_console_kthreads(int timeout_ms); /* * Please don't use printk_ratelimit(), because it shares ratelimiting state @@ -238,6 +239,10 @@ static inline bool pr_flush(int timeout_ms, bool reset_on_progress) return true; } +static inline void try_block_console_kthreads(int timeout_ms) +{ +} + static inline int printk_ratelimit(void) { return 0; diff --git a/kernel/panic.c b/kernel/panic.c index 6737b2332275..fe73d18ecdf0 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -273,6 +273,7 @@ void panic(const char *fmt, ...) * unfortunately means it may not be hardened to work in a * panic situation. */ + try_block_console_kthreads(10000); smp_send_stop(); } else { /* @@ -280,6 +281,7 @@ void panic(const char *fmt, ...) * kmsg_dump, we will need architecture dependent extra * works in addition to stopping other CPUs. */ + try_block_console_kthreads(10000); crash_smp_send_stop(); } diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index d947ca6c84f9..e7d8578860ad 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -20,6 +20,8 @@ enum printk_info_flags { LOG_CONT = 8, /* text is a fragment of a continuation line */ }; +extern bool block_console_kthreads; + __printf(4, 0) int vprintk_store(int facility, int level, const struct dev_printk_info *dev_info, diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 45c6c2b0b104..b095fb5f5f61 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -250,6 +250,9 @@ static atomic_t console_kthreads_active = ATOMIC_INIT(0); #define console_kthread_printing_exit() \ atomic_dec(&console_kthreads_active) +/* Block console kthreads to avoid processing new messages. */ +bool block_console_kthreads; + /* * Helper macros to handle lockdep when locking/unlocking console_sem. We use * macros instead of functions so that _RET_IP_ contains useful information. @@ -3730,6 +3733,7 @@ static bool printer_should_wake(struct console *con, u64 seq) if (con->blocked || console_kthreads_atomically_blocked() || + block_console_kthreads || system_state > SYSTEM_RUNNING || oops_in_progress) { return false; diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index ef0f9a2044da..caac4de1ea59 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -8,7 +8,9 @@ #include #include #include +#include #include +#include #include "internal.h" @@ -50,3 +52,33 @@ asmlinkage int vprintk(const char *fmt, va_list args) return vprintk_default(fmt, args); } EXPORT_SYMBOL(vprintk); + +/** + * try_block_console_kthreads() - Try to block console kthreads and + * make the global console_lock() avaialble + * + * @timeout_ms: The maximum time (in ms) to wait. + * + * Prevent console kthreads from starting processing new messages. Wait + * until the global console_lock() become available. + * + * Context: Can be called in any context. + */ +void try_block_console_kthreads(int timeout_ms) +{ + block_console_kthreads = true; + + /* Do not wait when the console lock could not be safely taken. */ + if (this_cpu_read(printk_context) || in_nmi()) + return; + + while (timeout_ms > 0) { + if (console_trylock()) { + console_unlock(); + return; + } + + udelay(1000); + timeout_ms -= 1; + } +} diff --git a/kernel/reboot.c b/kernel/reboot.c index 4177645e74d6..310363685502 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -74,6 +74,7 @@ void kernel_restart_prepare(char *cmd) { blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd); system_state = SYSTEM_RESTART; + try_block_console_kthreads(10000); usermodehelper_disable(); device_shutdown(); } @@ -262,6 +263,7 @@ static void kernel_shutdown_prepare(enum system_states state) blocking_notifier_call_chain(&reboot_notifier_list, (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL); system_state = state; + try_block_console_kthreads(10000); usermodehelper_disable(); device_shutdown(); } -- cgit v1.2.3 From 20fb0c8272bbb102d15bdd11aa64f828619dd7cc Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Thu, 23 Jun 2022 16:51:52 +0200 Subject: Revert "printk: Wait for the global console lock when the system is going down" This reverts commit b87f02307d3cfbda768520f0687c51ca77e14fc3. The testing of 5.19 release candidates revealed missing synchronization between early and regular console functionality. It would be possible to start the console kthreads later as a workaround. But it is clear that console lock serialized console drivers between each other. It opens a big area of possible problems that were not considered by people involved in the development and review. printk() is crucial for debugging kernel issues and console output is very important part of it. The number of consoles is huge and a proper review would take some time. As a result it need to be reverted for 5.19. Link: https://lore.kernel.org/r/YrBdjVwBOVgLfHyb@alley Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220623145157.21938-2-pmladek@suse.com --- include/linux/printk.h | 5 ----- kernel/panic.c | 2 -- kernel/printk/internal.h | 2 -- kernel/printk/printk.c | 4 ---- kernel/printk/printk_safe.c | 32 -------------------------------- kernel/reboot.c | 2 -- 6 files changed, 47 deletions(-) (limited to 'kernel/panic.c') diff --git a/include/linux/printk.h b/include/linux/printk.h index c1e07c0652c7..cd26aab0ab2a 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -174,7 +174,6 @@ extern void printk_prefer_direct_enter(void); extern void printk_prefer_direct_exit(void); extern bool pr_flush(int timeout_ms, bool reset_on_progress); -extern void try_block_console_kthreads(int timeout_ms); /* * Please don't use printk_ratelimit(), because it shares ratelimiting state @@ -239,10 +238,6 @@ static inline bool pr_flush(int timeout_ms, bool reset_on_progress) return true; } -static inline void try_block_console_kthreads(int timeout_ms) -{ -} - static inline int printk_ratelimit(void) { return 0; diff --git a/kernel/panic.c b/kernel/panic.c index fe73d18ecdf0..6737b2332275 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -273,7 +273,6 @@ void panic(const char *fmt, ...) * unfortunately means it may not be hardened to work in a * panic situation. */ - try_block_console_kthreads(10000); smp_send_stop(); } else { /* @@ -281,7 +280,6 @@ void panic(const char *fmt, ...) * kmsg_dump, we will need architecture dependent extra * works in addition to stopping other CPUs. */ - try_block_console_kthreads(10000); crash_smp_send_stop(); } diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index e7d8578860ad..d947ca6c84f9 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -20,8 +20,6 @@ enum printk_info_flags { LOG_CONT = 8, /* text is a fragment of a continuation line */ }; -extern bool block_console_kthreads; - __printf(4, 0) int vprintk_store(int facility, int level, const struct dev_printk_info *dev_info, diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index b095fb5f5f61..45c6c2b0b104 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -250,9 +250,6 @@ static atomic_t console_kthreads_active = ATOMIC_INIT(0); #define console_kthread_printing_exit() \ atomic_dec(&console_kthreads_active) -/* Block console kthreads to avoid processing new messages. */ -bool block_console_kthreads; - /* * Helper macros to handle lockdep when locking/unlocking console_sem. We use * macros instead of functions so that _RET_IP_ contains useful information. @@ -3733,7 +3730,6 @@ static bool printer_should_wake(struct console *con, u64 seq) if (con->blocked || console_kthreads_atomically_blocked() || - block_console_kthreads || system_state > SYSTEM_RUNNING || oops_in_progress) { return false; diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index caac4de1ea59..ef0f9a2044da 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -8,9 +8,7 @@ #include #include #include -#include #include -#include #include "internal.h" @@ -52,33 +50,3 @@ asmlinkage int vprintk(const char *fmt, va_list args) return vprintk_default(fmt, args); } EXPORT_SYMBOL(vprintk); - -/** - * try_block_console_kthreads() - Try to block console kthreads and - * make the global console_lock() avaialble - * - * @timeout_ms: The maximum time (in ms) to wait. - * - * Prevent console kthreads from starting processing new messages. Wait - * until the global console_lock() become available. - * - * Context: Can be called in any context. - */ -void try_block_console_kthreads(int timeout_ms) -{ - block_console_kthreads = true; - - /* Do not wait when the console lock could not be safely taken. */ - if (this_cpu_read(printk_context) || in_nmi()) - return; - - while (timeout_ms > 0) { - if (console_trylock()) { - console_unlock(); - return; - } - - udelay(1000); - timeout_ms -= 1; - } -} diff --git a/kernel/reboot.c b/kernel/reboot.c index 310363685502..4177645e74d6 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -74,7 +74,6 @@ void kernel_restart_prepare(char *cmd) { blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd); system_state = SYSTEM_RESTART; - try_block_console_kthreads(10000); usermodehelper_disable(); device_shutdown(); } @@ -263,7 +262,6 @@ static void kernel_shutdown_prepare(enum system_states state) blocking_notifier_call_chain(&reboot_notifier_list, (state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL); system_state = state; - try_block_console_kthreads(10000); usermodehelper_disable(); device_shutdown(); } -- cgit v1.2.3 From 07a22b61946f0b80065b0ddcc703b715f84355f5 Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Thu, 23 Jun 2022 16:51:57 +0200 Subject: Revert "printk: add functions to prefer direct printing" This reverts commit 2bb2b7b57f81255c13f4395ea911d6bdc70c9fe2. The testing of 5.19 release candidates revealed missing synchronization between early and regular console functionality. It would be possible to start the console kthreads later as a workaround. But it is clear that console lock serialized console drivers between each other. It opens a big area of possible problems that were not considered by people involved in the development and review. printk() is crucial for debugging kernel issues and console output is very important part of it. The number of consoles is huge and a proper review would take some time. As a result it need to be reverted for 5.19. Link: https://lore.kernel.org/r/YrBdjVwBOVgLfHyb@alley Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220623145157.21938-7-pmladek@suse.com --- drivers/tty/sysrq.c | 2 -- include/linux/printk.h | 11 ----------- kernel/hung_task.c | 11 +---------- kernel/panic.c | 4 ---- kernel/printk/printk.c | 28 ---------------------------- kernel/rcu/tree_stall.h | 2 -- kernel/reboot.c | 14 +------------- kernel/watchdog.c | 4 ---- kernel/watchdog_hld.c | 4 ---- 9 files changed, 2 insertions(+), 78 deletions(-) (limited to 'kernel/panic.c') diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 2884cd638d64..bbfd004449b5 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -578,7 +578,6 @@ void __handle_sysrq(int key, bool check_mask) rcu_sysrq_start(); rcu_read_lock(); - printk_prefer_direct_enter(); /* * Raise the apparent loglevel to maximum so that the sysrq header * is shown to provide the user with positive feedback. We do not @@ -620,7 +619,6 @@ void __handle_sysrq(int key, bool check_mask) pr_cont("\n"); console_loglevel = orig_log_level; } - printk_prefer_direct_exit(); rcu_read_unlock(); rcu_sysrq_end(); diff --git a/include/linux/printk.h b/include/linux/printk.h index cd26aab0ab2a..091fba7283e1 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -170,9 +170,6 @@ extern void __printk_safe_exit(void); #define printk_deferred_enter __printk_safe_enter #define printk_deferred_exit __printk_safe_exit -extern void printk_prefer_direct_enter(void); -extern void printk_prefer_direct_exit(void); - extern bool pr_flush(int timeout_ms, bool reset_on_progress); /* @@ -225,14 +222,6 @@ static inline void printk_deferred_exit(void) { } -static inline void printk_prefer_direct_enter(void) -{ -} - -static inline void printk_prefer_direct_exit(void) -{ -} - static inline bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 02a65d554340..52501e5f7655 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -127,8 +127,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) * complain: */ if (sysctl_hung_task_warnings) { - printk_prefer_direct_enter(); - if (sysctl_hung_task_warnings > 0) sysctl_hung_task_warnings--; pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", @@ -144,8 +142,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) if (sysctl_hung_task_all_cpu_backtrace) hung_task_show_all_bt = true; - - printk_prefer_direct_exit(); } touch_nmi_watchdog(); @@ -208,17 +204,12 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) } unlock: rcu_read_unlock(); - if (hung_task_show_lock) { - printk_prefer_direct_enter(); + if (hung_task_show_lock) debug_show_all_locks(); - printk_prefer_direct_exit(); - } if (hung_task_show_all_bt) { hung_task_show_all_bt = false; - printk_prefer_direct_enter(); trigger_all_cpu_backtrace(); - printk_prefer_direct_exit(); } if (hung_task_call_panic) diff --git a/kernel/panic.c b/kernel/panic.c index 6737b2332275..8355b19676f8 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -579,8 +579,6 @@ void __warn(const char *file, int line, void *caller, unsigned taint, { disable_trace_on_warning(); - printk_prefer_direct_enter(); - if (file) pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n", raw_smp_processor_id(), current->pid, file, line, @@ -610,8 +608,6 @@ void __warn(const char *file, int line, void *caller, unsigned taint, /* Just a warning, don't kill lockdep. */ add_taint(taint, LOCKDEP_STILL_OK); - - printk_prefer_direct_exit(); } #ifndef __WARN_FLAGS diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 5a6273e56b4e..b49c6ff6dca0 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -362,34 +362,6 @@ static int console_msg_format = MSG_FORMAT_DEFAULT; static DEFINE_MUTEX(syslog_lock); #ifdef CONFIG_PRINTK -static atomic_t printk_prefer_direct = ATOMIC_INIT(0); - -/** - * printk_prefer_direct_enter - cause printk() calls to attempt direct - * printing to all enabled consoles - * - * Since it is not possible to call into the console printing code from any - * context, there is no guarantee that direct printing will occur. - * - * This globally effects all printk() callers. - * - * Context: Any context. - */ -void printk_prefer_direct_enter(void) -{ - atomic_inc(&printk_prefer_direct); -} - -/** - * printk_prefer_direct_exit - restore printk() behavior - * - * Context: Any context. - */ -void printk_prefer_direct_exit(void) -{ - WARN_ON(atomic_dec_if_positive(&printk_prefer_direct) < 0); -} - DECLARE_WAIT_QUEUE_HEAD(log_wait); /* All 3 protected by @syslog_lock. */ /* the next printk record to read by syslog(READ) or /proc/kmsg */ diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 4995c078cff9..a001e1e7a992 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -647,7 +647,6 @@ static void print_cpu_stall(unsigned long gps) * See Documentation/RCU/stallwarn.rst for info on how to debug * RCU CPU stall warnings. */ - printk_prefer_direct_enter(); trace_rcu_stall_warning(rcu_state.name, TPS("SelfDetected")); pr_err("INFO: %s self-detected stall on CPU\n", rcu_state.name); raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags); @@ -685,7 +684,6 @@ static void print_cpu_stall(unsigned long gps) */ set_tsk_need_resched(current); set_preempt_need_resched(); - printk_prefer_direct_exit(); } static void check_cpu_stall(struct rcu_data *rdp) diff --git a/kernel/reboot.c b/kernel/reboot.c index 4177645e74d6..6bcc5d6a6572 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -447,11 +447,9 @@ static int __orderly_reboot(void) ret = run_cmd(reboot_cmd); if (ret) { - printk_prefer_direct_enter(); pr_warn("Failed to start orderly reboot: forcing the issue\n"); emergency_sync(); kernel_restart(NULL); - printk_prefer_direct_exit(); } return ret; @@ -464,7 +462,6 @@ static int __orderly_poweroff(bool force) ret = run_cmd(poweroff_cmd); if (ret && force) { - printk_prefer_direct_enter(); pr_warn("Failed to start orderly shutdown: forcing the issue\n"); /* @@ -474,7 +471,6 @@ static int __orderly_poweroff(bool force) */ emergency_sync(); kernel_power_off(); - printk_prefer_direct_exit(); } return ret; @@ -532,8 +528,6 @@ EXPORT_SYMBOL_GPL(orderly_reboot); */ static void hw_failure_emergency_poweroff_func(struct work_struct *work) { - printk_prefer_direct_enter(); - /* * We have reached here after the emergency shutdown waiting period has * expired. This means orderly_poweroff has not been able to shut off @@ -550,8 +544,6 @@ static void hw_failure_emergency_poweroff_func(struct work_struct *work) */ pr_emerg("Hardware protection shutdown failed. Trying emergency restart\n"); emergency_restart(); - - printk_prefer_direct_exit(); } static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work, @@ -590,13 +582,11 @@ void hw_protection_shutdown(const char *reason, int ms_until_forced) { static atomic_t allow_proceed = ATOMIC_INIT(1); - printk_prefer_direct_enter(); - pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason); /* Shutdown should be initiated only once. */ if (!atomic_dec_and_test(&allow_proceed)) - goto out; + return; /* * Queue a backup emergency shutdown in the event of @@ -604,8 +594,6 @@ void hw_protection_shutdown(const char *reason, int ms_until_forced) */ hw_failure_emergency_poweroff(ms_until_forced); orderly_poweroff(true); -out: - printk_prefer_direct_exit(); } EXPORT_SYMBOL_GPL(hw_protection_shutdown); diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 40024e03d422..9166220457bc 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -424,8 +424,6 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) /* Start period for the next softlockup warning. */ update_report_ts(); - printk_prefer_direct_enter(); - pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); @@ -444,8 +442,6 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); if (softlockup_panic) panic("softlockup: hung tasks"); - - printk_prefer_direct_exit(); } return HRTIMER_RESTART; diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c index 701f35f0e2d4..247bf0b1582c 100644 --- a/kernel/watchdog_hld.c +++ b/kernel/watchdog_hld.c @@ -135,8 +135,6 @@ static void watchdog_overflow_callback(struct perf_event *event, if (__this_cpu_read(hard_watchdog_warn) == true) return; - printk_prefer_direct_enter(); - pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n", this_cpu); print_modules(); @@ -157,8 +155,6 @@ static void watchdog_overflow_callback(struct perf_event *event, if (hardlockup_panic) nmi_panic(regs, "Hard LOCKUP"); - printk_prefer_direct_exit(); - __this_cpu_write(hard_watchdog_warn, true); return; } -- cgit v1.2.3 From 2852ca7fba9f77b204f0fe953b31fadd0057c936 Mon Sep 17 00:00:00 2001 From: David Gow Date: Fri, 1 Jul 2022 16:47:41 +0800 Subject: panic: Taint kernel if tests are run Most in-kernel tests (such as KUnit tests) are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (for example, KUnit assertions will often deliberately leak kernel addresses). Add a new taint type, TAINT_TEST to signal that a test has been run. This will be printed as 'N' (originally for kuNit, as every other sensible letter was taken.) This should discourage people from running these tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.) Acked-by: Luis Chamberlain Reviewed-by: Brendan Higgins Signed-off-by: David Gow Signed-off-by: Shuah Khan --- Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + 3 files changed, 4 insertions(+), 1 deletion(-) (limited to 'kernel/panic.c') diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..7d80e8c307d1 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin + 18 _/N 262144 an in-kernel test has been run === === ====== ======================================================== Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index e71161da69c4..c7759b3f2045 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -68,7 +68,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_TEST 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1) struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index a3c758dba15a..6b3369e21026 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -428,6 +428,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true }, + [ TAINT_TEST ] = { 'N', ' ', true }, }; /** -- cgit v1.2.3 From 0a64ce6e5442bbd96cbe9057d9ba1edab244f25b Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Tue, 30 Aug 2022 16:50:04 +0200 Subject: kernel/panic: Drop unblank_screen call MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit console_unblank() does this too (called in both places right after), and with a lot more confidence inspiring approach to locking. Reconstructing this story is very strange: In b61312d353da ("oops handling: ensure that any oops is flushed to the mtdoops console") it is claimed that a printk(" "); flushed out the console buffer, which was removed in e3e8a75d2acf ("[PATCH] Extract and use wake_up_klogd()"). In todays kernels this is done way earlier in console_flush_on_panic with some really nasty tricks. I didn't bother to fully reconstruct this all, least because the call to bust_spinlock(0); gets moved every few years, depending upon how the wind blows (or well, who screamed loudest about the various issue each call site caused). Before that commit the only calls to console_unblank() where in s390 arch code. The other side here is the console->unblank callback, which was introduced in 2.1.31 for the vt driver. Which predates the console_unblank() function by a lot, which was added (without users) in 2.4.14.3. So pretty much impossible to guess at any motivation here. Also afaict the vt driver is the only (and always was the only) console driver implementing the unblank callback, so no idea why a call to console_unblank() was added for the mtdooops driver - the action actually flushing out the console buffers is done from console_unlock() only. Note that as prep for the s390 users the locking was adjusted in 2.5.22 (I couldn't figure out how to properly reference the BK commit from the historical git trees) from a normal semaphore to a trylock. Note that a copy of the direct unblank_screen() call was added to panic() in c7c3f05e341a ("panic: avoid deadlocks in re-entrant console drivers"), which partially inlined the bust_spinlocks(0); call. Long story short, I have no idea why the direct call to unblank_screen survived for so long (the infrastructure to do it properly existed for years), nor why it wasn't removed when the console_unblank() call was finally added. But it makes a ton more sense to finally do that than not - it's just better encapsulation to go through the console functions instead of doing a direct call, so let's dare. Plus it really does not make much sense to call the only unblank implementation there is twice, once without, and once with appropriate locking. Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: Daniel Vetter Cc: "Ilpo Järvinen" Cc: Tetsuo Handa Cc: Xuezhi Zhang Cc: Yangxi Xiang Cc: nick black Cc: Petr Mladek Cc: Andrew Morton Cc: Luis Chamberlain Cc: "Guilherme G. Piccoli" Cc: Marco Elver Cc: John Ogness Cc: Sebastian Andrzej Siewior Cc: David Gow Cc: tangmeng Cc: Tiezhu Yang Cc: Chris Wilson Reviewed-by: Petr Mladek Acked-by: Sebastian Andrzej Siewior Signed-off-by: Daniel Vetter Signed-off-by: Andrew Morton Link: https://lore.kernel.org/r/20220830145004.430545-1-daniel.vetter@ffwll.ch Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/vt.c | 3 ++- include/linux/vt_kern.h | 1 - kernel/panic.c | 3 --- lib/bust_spinlocks.c | 3 --- 4 files changed, 2 insertions(+), 8 deletions(-) (limited to 'kernel/panic.c') diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 4d29e4a17db7..2cb515dbda53 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -154,6 +154,7 @@ static void console_callback(struct work_struct *ignored); static void con_driver_unregister_callback(struct work_struct *ignored); static void blank_screen_t(struct timer_list *unused); static void set_palette(struct vc_data *vc); +static void unblank_screen(void); #define vt_get_kmsg_redirect() vt_kmsg_redirect(-1) @@ -4448,7 +4449,7 @@ EXPORT_SYMBOL(do_unblank_screen); * call it with 1 as an argument and so force a mode restore... that may kill * X or at least garbage the screen but would also make the Oops visible... */ -void unblank_screen(void) +static void unblank_screen(void) { do_unblank_screen(0); } diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h index b5ab452fca5b..c1f5aebef170 100644 --- a/include/linux/vt_kern.h +++ b/include/linux/vt_kern.h @@ -30,7 +30,6 @@ struct vc_data *vc_deallocate(unsigned int console); void reset_palette(struct vc_data *vc); void do_blank_screen(int entering_gfx); void do_unblank_screen(int leaving_gfx); -void unblank_screen(void); void poke_blanked_console(void); int con_font_op(struct vc_data *vc, struct console_font_op *op); int con_set_cmap(unsigned char __user *cmap); diff --git a/kernel/panic.c b/kernel/panic.c index c6eb8f8db0c0..da323209f583 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -329,9 +329,6 @@ void panic(const char *fmt, ...) if (_crash_kexec_post_notifiers) __crash_kexec(NULL); -#ifdef CONFIG_VT - unblank_screen(); -#endif console_unblank(); /* diff --git a/lib/bust_spinlocks.c b/lib/bust_spinlocks.c index 8be59f84eaea..bfd53972a4d8 100644 --- a/lib/bust_spinlocks.c +++ b/lib/bust_spinlocks.c @@ -22,9 +22,6 @@ void bust_spinlocks(int yes) if (yes) { ++oops_in_progress; } else { -#ifdef CONFIG_VT - unblank_screen(); -#endif console_unblank(); if (--oops_in_progress == 0) wake_up_klogd(); -- cgit v1.2.3