linux/kernel/sys.c, branch v5.0

kernel/sys.c: Clarify that UNAME26 does not generate unique versions anymore

2019-01-13T22:38:03Z

UNAME26 is a mechanism to report Linux's version as 2.6.x, for compatibility with old/broken software. Due to the way it is implemented, it would have to be updated after 5.0, to keep the resulting versions unique. Linus Torvalds argued: "Do we actually need this? I'd rather let it bitrot, and just let it return random versions. It will just start again at 2.4.60, won't it? Anybody who uses UNAME26 for a 5.x kernel might as well think it's still 4.x. The user space is so old that it can't possibly care about differences between 4.x and 5.x, can it? The only thing that matters is that it shows "2.4.", which it will do regardless" Signed-off-by: Jonathan Neuschäfer Signed-off-by: Linus Torvalds

Remove 'type' argument from access_ok() function

2019-01-04T02:57:57Z

Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds

arm64: add prctl control for resetting ptrauth keys

2018-12-13T16:42:46Z

Add an arm64-specific prctl to allow a thread to reinitialize its pointer authentication keys to random values. This can be useful when exec() is not used for starting new processes, to ensure that different processes still have different keys. Signed-off-by: Kristina Martsenko Signed-off-by: Will Deacon

kernel/sys.c: remove duplicated include

2018-09-20T20:01:11Z

Link: http://lkml.kernel.org/r/20180821133424.18716-1-yuehaibing@huawei.com Signed-off-by: YueHaibing Reviewed-by: Andrew Morton Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2018-08-24T16:25:39Z

Pull namespace fixes from Eric Biederman: "This is a set of four fairly obvious bug fixes: - a switch from d_find_alias to d_find_any_alias because the xattr code perversely takes a dentry - two mutex vs copy_to_user fixes from Jann Horn - a fix to use a sanitized size not the size userspace passed in from Christian Brauner" * 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: getxattr: use correct xattr length sys: don't hold uts_sem while accessing userspace memory userns: move user access out of the mutex cap_inode_getsecurity: use d_find_any_alias() instead of d_find_alias()

sys: don't hold uts_sem while accessing userspace memory

2018-08-11T07:05:53Z

Holding uts_sem as a writer while accessing userspace memory allows a namespace admin to stall all processes that attempt to take uts_sem. Instead, move data through stack buffers and don't access userspace memory while uts_sem is held. Cc: stable@vger.kernel.org Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Jann Horn Signed-off-by: Eric W. Biederman

sysinfo: Remove get_monotonic_boottime()

2018-06-19T07:56:27Z

get_monotonic_boottime() is deprecated because it uses the old 'timespec' structure. This replaces one of the last callers with a call to ktime_get_boottime. Signed-off-by: Arnd Bergmann Signed-off-by: Thomas Gleixner Reviewed-by: Cyrill Gorcunov Cc: Andrew Morton Cc: y2038@lists.linaro.org Cc: Dominik Brodowski Cc: Cyrill Gorcunov Link: https://lkml.kernel.org/r/20180618150114.849216-1-arnd@arndb.de

mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct

2018-06-08T00:34:34Z

mmap_sem is on the hot path of kernel, and it very contended, but it is abused too. It is used to protect arg_start|end and evn_start|end when reading /proc/$PID/cmdline and /proc/$PID/environ, but it doesn't make sense since those proc files just expect to read 4 values atomically and not related to VM, they could be set to arbitrary values by C/R. And, the mmap_sem contention may cause unexpected issue like below: INFO: task ps:14018 blocked for more than 120 seconds. Tainted: G E 4.9.79-009.ali3000.alios7.x86_64 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. ps D 0 14018 1 0x00000004 Call Trace: schedule+0x36/0x80 rwsem_down_read_failed+0xf0/0x150 call_rwsem_down_read_failed+0x18/0x30 down_read+0x20/0x40 proc_pid_cmdline_read+0xd9/0x4e0 __vfs_read+0x37/0x150 vfs_read+0x96/0x130 SyS_read+0x55/0xc0 entry_SYSCALL_64_fastpath+0x1a/0xc5 Both Alexey Dobriyan and Michal Hocko suggested to use dedicated lock for them to mitigate the abuse of mmap_sem. So, introduce a new spinlock in mm_struct to protect the concurrent access to arg_start|end, env_start|end and others, as well as replace write map_sem to read to protect the race condition between prctl and sys_brk which might break check_data_rlimit(), and makes prctl more friendly to other VM operations. This patch just eliminates the abuse of mmap_sem, but it can't resolve the above hung task warning completely since the later access_remote_vm() call needs acquire mmap_sem. The mmap_sem scalability issue will be solved in the future. [yang.shi@linux.alibaba.com: add comment about mmap_sem and arg_lock] Link: http://lkml.kernel.org/r/1524077799-80690-1-git-send-email-yang.shi@linux.alibaba.com Link: http://lkml.kernel.org/r/1523730291-109696-1-git-send-email-yang.shi@linux.alibaba.com Signed-off-by: Yang Shi Reviewed-by: Cyrill Gorcunov Acked-by: Michal Hocko Cc: Alexey Dobriyan Cc: Matthew Wilcox Cc: Mateusz Guzik Cc: Kirill Tkhai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/sys.c: fix potential Spectre v1 issue

2018-05-26T01:12:11Z

`resource' can be controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: kernel/sys.c:1474 __do_compat_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap) kernel/sys.c:1455 __do_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap) Fix this by sanitizing *resource* before using it to index current->signal->rlim Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Link: http://lkml.kernel.org/r/20180515030038.GA11822@embeddedor.com Signed-off-by: Gustavo A. R. Silva Reviewed-by: Andrew Morton Cc: Alexei Starovoitov Cc: Dan Williams Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

nospec: Allow getting/setting on non-current task

2018-05-03T11:55:51Z

Adjust arch_prctl_get/set_spec_ctrl() to operate on tasks other than current. This is needed both for /proc/$pid/status queries and for seccomp (since thread-syncing can trigger seccomp in non-current threads). Signed-off-by: Kees Cook Signed-off-by: Thomas Gleixner