linux/kernel/sys.c, branch v5.7

sys/sysinfo: Respect boottime inside time namespace

2020-03-03T18:34:32Z

The sysinfo() syscall includes uptime in seconds but has no correction for time namespaces which makes it inconsistent with the /proc/uptime inside of a time namespace. Add the missing time namespace adjustment call. Signed-off-by: Cyril Hrubis Signed-off-by: Thomas Gleixner Reviewed-by: Dmitry Safonov Link: https://lkml.kernel.org/r/20200303150638.7329-1-chrubis@suse.cz

prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim

2020-01-28T09:09:51Z

There are several storage drivers like dm-multipath, iscsi, tcmu-runner, amd nbd that have userspace components that can run in the IO path. For example, iscsi and nbd's userspace deamons may need to recreate a socket and/or send IO on it, and dm-multipath's daemon multipathd may need to send SG IO or read/write IO to figure out the state of paths and re-set them up. In the kernel these drivers have access to GFP_NOIO/GFP_NOFS and the memalloc_*_save/restore functions to control the allocation behavior, but for userspace we would end up hitting an allocation that ended up writing data back to the same device we are trying to allocate for. The device is then in a state of deadlock, because to execute IO the device needs to allocate memory, but to allocate memory the memory layers want execute IO to the device. Here is an example with nbd using a local userspace daemon that performs network IO to a remote server. We are using XFS on top of the nbd device, but it can happen with any FS or other modules layered on top of the nbd device that can write out data to free memory. Here a nbd daemon helper thread, msgr-worker-1, is performing a write/sendmsg on a socket to execute a request. This kicks off a reclaim operation which results in a WRITE to the nbd device and the nbd thread calling back into the mm layer. [ 1626.609191] msgr-worker-1 D 0 1026 1 0x00004000 [ 1626.609193] Call Trace: [ 1626.609195] ? __schedule+0x29b/0x630 [ 1626.609197] ? wait_for_completion+0xe0/0x170 [ 1626.609198] schedule+0x30/0xb0 [ 1626.609200] schedule_timeout+0x1f6/0x2f0 [ 1626.609202] ? blk_finish_plug+0x21/0x2e [ 1626.609204] ? _xfs_buf_ioapply+0x2e6/0x410 [ 1626.609206] ? wait_for_completion+0xe0/0x170 [ 1626.609208] wait_for_completion+0x108/0x170 [ 1626.609210] ? wake_up_q+0x70/0x70 [ 1626.609212] ? __xfs_buf_submit+0x12e/0x250 [ 1626.609214] ? xfs_bwrite+0x25/0x60 [ 1626.609215] xfs_buf_iowait+0x22/0xf0 [ 1626.609218] __xfs_buf_submit+0x12e/0x250 [ 1626.609220] xfs_bwrite+0x25/0x60 [ 1626.609222] xfs_reclaim_inode+0x2e8/0x310 [ 1626.609224] xfs_reclaim_inodes_ag+0x1b6/0x300 [ 1626.609227] xfs_reclaim_inodes_nr+0x31/0x40 [ 1626.609228] super_cache_scan+0x152/0x1a0 [ 1626.609231] do_shrink_slab+0x12c/0x2d0 [ 1626.609233] shrink_slab+0x9c/0x2a0 [ 1626.609235] shrink_node+0xd7/0x470 [ 1626.609237] do_try_to_free_pages+0xbf/0x380 [ 1626.609240] try_to_free_pages+0xd9/0x1f0 [ 1626.609245] __alloc_pages_slowpath+0x3a4/0xd30 [ 1626.609251] ? ___slab_alloc+0x238/0x560 [ 1626.609254] __alloc_pages_nodemask+0x30c/0x350 [ 1626.609259] skb_page_frag_refill+0x97/0xd0 [ 1626.609274] sk_page_frag_refill+0x1d/0x80 [ 1626.609279] tcp_sendmsg_locked+0x2bb/0xdd0 [ 1626.609304] tcp_sendmsg+0x27/0x40 [ 1626.609307] sock_sendmsg+0x54/0x60 [ 1626.609308] ___sys_sendmsg+0x29f/0x320 [ 1626.609313] ? sock_poll+0x66/0xb0 [ 1626.609318] ? ep_item_poll.isra.15+0x40/0xc0 [ 1626.609320] ? ep_send_events_proc+0xe6/0x230 [ 1626.609322] ? hrtimer_try_to_cancel+0x54/0xf0 [ 1626.609324] ? ep_read_events_proc+0xc0/0xc0 [ 1626.609326] ? _raw_write_unlock_irq+0xa/0x20 [ 1626.609327] ? ep_scan_ready_list.constprop.19+0x218/0x230 [ 1626.609329] ? __hrtimer_init+0xb0/0xb0 [ 1626.609331] ? _raw_spin_unlock_irq+0xa/0x20 [ 1626.609334] ? ep_poll+0x26c/0x4a0 [ 1626.609337] ? tcp_tsq_write.part.54+0xa0/0xa0 [ 1626.609339] ? release_sock+0x43/0x90 [ 1626.609341] ? _raw_spin_unlock_bh+0xa/0x20 [ 1626.609342] __sys_sendmsg+0x47/0x80 [ 1626.609347] do_syscall_64+0x5f/0x1c0 [ 1626.609349] ? prepare_exit_to_usermode+0x75/0xa0 [ 1626.609351] entry_SYSCALL_64_after_hwframe+0x44/0xa9 This patch adds a new prctl command that daemons can use after they have done their initial setup, and before they start to do allocations that are in the IO path. It sets the PF_MEMALLOC_NOIO and PF_LESS_THROTTLE flags so both userspace block and FS threads can use it to avoid the allocation recursion and try to prevent from being throttled while writing out data to free up memory. Signed-off-by: Mike Christie Acked-by: Michal Hocko Tested-by: Masato Suzuki Reviewed-by: Damien Le Moal Reviewed-by: Bart Van Assche Reviewed-by: Dave Chinner Reviewed-by: Darrick J. Wong Link: https://lore.kernel.org/r/20191112001900.9206-1-mchristi@redhat.com Signed-off-by: Christian Brauner

kernel/sys.c: avoid copying possible padding bytes in copy_to_user

2019-12-05T03:44:12Z

Initialization is not guaranteed to zero padding bytes so use an explicit memset instead to avoid leaking any kernel content in any possible padding bytes. Link: http://lkml.kernel.org/r/dfa331c00881d61c8ee51577a082d8bebd61805c.camel@perches.com Signed-off-by: Joe Perches Cc: Dan Carpenter Cc: Julia Lawall Cc: Thomas Gleixner Cc: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

y2038: rusage: use __kernel_old_timeval

2019-11-15T13:38:29Z

There are two 'struct timeval' fields in 'struct rusage'. Unfortunately the definition of timeval is now ambiguous when used in user space with a libc that has a 64-bit time_t, and this also changes the 'rusage' definition in user space in a way that is incompatible with the system call interface. While there is no good solution to avoid all ambiguity here, change the definition in the kernel headers to be compatible with the kernel ABI, using __kernel_old_timeval as an unambiguous base type. In previous discussions, there was also a plan to add a replacement for rusage based on 64-bit timestamps and nanosecond resolution, i.e. 'struct __kernel_timespec'. I have patches for that as well, if anyone thinks we should do that. Reviewed-by: Cyrill Gorcunov Signed-off-by: Arnd Bergmann

Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-09-17T19:35:15Z

Pull core timer updates from Thomas Gleixner: "Timers and timekeeping updates: - A large overhaul of the posix CPU timer code which is a preparation for moving the CPU timer expiry out into task work so it can be properly accounted on the task/process. An update to the bogus permission checks will come later during the merge window as feedback was not complete before heading of for travel. - Switch the timerqueue code to use cached rbtrees and get rid of the homebrewn caching of the leftmost node. - Consolidate hrtimer_init() + hrtimer_init_sleeper() calls into a single function - Implement the separation of hrtimers to be forced to expire in hard interrupt context even when PREEMPT_RT is enabled and mark the affected timers accordingly. - Implement a mechanism for hrtimers and the timer wheel to protect RT against priority inversion and live lock issues when a (hr)timer which should be canceled is currently executing the callback. Instead of infinitely spinning, the task which tries to cancel the timer blocks on a per cpu base expiry lock which is held and released by the (hr)timer expiry code. - Enable the Hyper-V TSC page based sched_clock for Hyper-V guests resulting in faster access to timekeeping functions. - Updates to various clocksource/clockevent drivers and their device tree bindings. - The usual small improvements all over the place" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (101 commits) posix-cpu-timers: Fix permission check regression posix-cpu-timers: Always clear head pointer on dequeue hrtimer: Add a missing bracket and hide `migration_base' on !SMP posix-cpu-timers: Make expiry_active check actually work correctly posix-timers: Unbreak CONFIG_POSIX_TIMERS=n build tick: Mark sched_timer to expire in hard interrupt context hrtimer: Add kernel doc annotation for HRTIMER_MODE_HARD x86/hyperv: Hide pv_ops access for CONFIG_PARAVIRT=n posix-cpu-timers: Utilize timerqueue for storage posix-cpu-timers: Move state tracking to struct posix_cputimers posix-cpu-timers: Deduplicate rlimit handling posix-cpu-timers: Remove pointless comparisons posix-cpu-timers: Get rid of 64bit divisions posix-cpu-timers: Consolidate timer expiry further posix-cpu-timers: Get rid of zero checks rlimit: Rewrite non-sensical RLIMIT_CPU comment posix-cpu-timers: Respect INFINITY for hard RTTIME limit posix-cpu-timers: Switch thread group sampling to array posix-cpu-timers: Restructure expiry array posix-cpu-timers: Remove cputime_expires ...

Merge branch 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-09-17T01:47:53Z

Pull x86 cpu-feature updates from Ingo Molnar: - Rework the Intel model names symbols/macros, which were decades of ad-hoc extensions and added random noise. It's now a coherent, easy to follow nomenclature. - Add new Intel CPU model IDs: - "Tiger Lake" desktop and mobile models - "Elkhart Lake" model ID - and the "Lightning Mountain" variant of Airmont, plus support code - Add the new AVX512_VP2INTERSECT instruction to cpufeatures - Remove Intel MPX user-visible APIs and the self-tests, because the toolchain (gcc) is not supporting it going forward. This is the first, lowest-risk phase of MPX removal. - Remove X86_FEATURE_MFENCE_RDTSC - Various smaller cleanups and fixes * 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits) x86/cpu: Update init data for new Airmont CPU model x86/cpu: Add new Airmont variant to Intel family x86/cpu: Add Elkhart Lake to Intel family x86/cpu: Add Tiger Lake to Intel family x86: Correct misc typos x86/intel: Add common OPTDIFFs x86/intel: Aggregate microserver naming x86/intel: Aggregate big core graphics naming x86/intel: Aggregate big core mobile naming x86/intel: Aggregate big core client naming x86/cpufeature: Explain the macro duplication x86/ftrace: Remove mcount() declaration x86/PCI: Remove superfluous returns from void functions x86/msr-index: Move AMD MSRs where they belong x86/cpu: Use constant definitions for CPU models lib: Remove redundant ftrace flag removal x86/crash: Remove unnecessary comparison x86/bitops: Use __builtin_constant_p() directly instead of IS_IMMEDIATE() x86: Remove X86_FEATURE_MFENCE_RDTSC x86/mpx: Remove MPX APIs ...

posix-cpu-timers: Get rid of zero checks

2019-08-28T09:50:40Z

Deactivation of the expiry cache is done by setting all clock caches to 0. That requires to have a check for zero in all places which update the expiry cache: if (cache == 0 || new < cache) cache = new; Use U64_MAX as the deactivated value, which allows to remove the zero checks when updating the cache and reduces it to the obvious check: if (new < cache) cache = new; This also removes the weird workaround in do_prlimit() which was required to convert a RLIMIT_CPU value of 0 (immediate expiry) to 1 because handing in 0 to the posix CPU timer code would have effectively disarmed it. Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lkml.kernel.org/r/20190821192922.275086128@linutronix.de

rlimit: Rewrite non-sensical RLIMIT_CPU comment

2019-08-28T09:50:40Z

The comment above the function which arms RLIMIT_CPU in the posix CPU timer code makes no sense at all. It claims that the kernel does not return an error code when it rejected the attempt to set RLIMIT_CPU. That's clearly bogus as the code does an error check and the rlimit is only set and activated when the permission checks are ok. In case of a rejection an appropriate error code is returned. This is a historical and outdated comment which got dragged along even when the rlimit handling code was rewritten. Replace it with an explanation why the setup function is not called when the rlimit value is RLIM_INFINITY and how the 'disarming' is handled. Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lkml.kernel.org/r/20190821192922.185511287@linutronix.de

arm64: Tighten the PR_{SET, GET}_TAGGED_ADDR_CTRL prctl() unused arguments

2019-08-20T17:17:55Z

Require that arg{3,4,5} of the PR_{SET,GET}_TAGGED_ADDR_CTRL prctl and arg2 of the PR_GET_TAGGED_ADDR_CTRL prctl() are zero rather than ignored for future extensions. Acked-by: Andrey Konovalov Signed-off-by: Catalin Marinas Signed-off-by: Will Deacon

arm64: Introduce prctl() options to control the tagged user addresses ABI

2019-08-06T17:08:45Z

It is not desirable to relax the ABI to allow tagged user addresses into the kernel indiscriminately. This patch introduces a prctl() interface for enabling or disabling the tagged ABI with a global sysctl control for preventing applications from enabling the relaxed ABI (meant for testing user-space prctl() return error checking without reconfiguring the kernel). The ABI properties are inherited by threads of the same application and fork()'ed children but cleared on execve(). A Kconfig option allows the overall disabling of the relaxed ABI. The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle MTE-specific settings like imprecise vs precise exceptions. Reviewed-by: Kees Cook Signed-off-by: Catalin Marinas Signed-off-by: Andrey Konovalov Signed-off-by: Will Deacon