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Anna-Maria Behnsen 79f8b28e85 timers: Annotate possible non critical data race of next_expiry 
Global timers could be expired remotely when the target CPU is idle. After
a remote timer expiry, the remote timer_base->next_expiry value is updated
while holding the timer_base->lock. When the formerly idle CPU becomes
active at the same time and checks whether timers need to expire, this
check is done lockless as it is on the local CPU. This could lead to a data
race, which was reported by sysbot:

  https://lore.kernel.org/r/000000000000916e55061f969e14@google.com

When the value is read lockless but changed by the remote CPU, only two non
critical scenarios could happen:

1) The already update value is read -> everything is perfect

2) The old value is read -> a superfluous timer soft interrupt is raised

The same situation could happen when enqueueing a new first pinned timer by
a remote CPU also with non critical scenarios:

1) The already update value is read -> everything is perfect

2) The old value is read -> when the CPU is idle, an IPI is executed
nevertheless and when the CPU isn't idle, the updated value will be visible
on the next tick and the timer might be late one jiffie.

As this is very unlikely to happen, the overhead of doing the check under
the lock is a way more effort, than a superfluous timer soft interrupt or a
possible 1 jiffie delay of the timer.

Document and annotate this non critical behavior in the code by using
READ/WRITE_ONCE() pair when accessing timer_base->next_expiry.

Reported-by: syzbot+bf285fcc0a048e028118@syzkaller.appspotmail.com
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20240829154305.19259-1-anna-maria@linutronix.de
Closes: https://lore.kernel.org/lkml/000000000000916e55061f969e14@google.com
 		2024-09-04 11:57:56 +02:00
..
bpf sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
cgroup Merge branch 'for-6.10-fixes' into for-6.11 2024-07-14 18:04:03 -10:00
configs mm/slab: Plumb kmem_buckets into __do_kmalloc_node() 2024-07-03 12:24:19 +02:00
debug kdb: Get rid of redundant kdb_curr_task() 2024-06-21 15:49:29 +01:00
dma dma: fix call order in dmam_free_coherent 2024-07-19 07:27:28 +02:00
entry entry: Respect changes to system call number by trace_sys_enter() 2024-03-12 13:23:32 +01:00
events A lot of networking people were at a conference last week, busy 2024-07-25 13:32:25 -07:00
futex printk: Change type of CONFIG_BASE_SMALL to bool 2024-05-06 17:39:09 +02:00
gcov gcov: add support for GCC 14 2024-06-15 10:43:06 -07:00
irq Switch ARM/ARM64 over to the modern per device MSI domains: 2024-07-22 14:02:19 -07:00
kcsan kcsan: Add missing MODULE_DESCRIPTION() macro 2024-06-06 11:21:14 -07:00
livepatch livepatch: Replace snprintf() with sysfs_emit() 2024-07-02 16:56:18 +02:00
locking bcachefs changes for 6.11-rc1 (version 2) 2024-07-18 17:27:43 -07:00
module bpf-next-for-netdev 2024-07-09 17:01:46 +02:00
power mm: remove the implementation of swap_free() and always use swap_free_nr() 2024-07-03 19:30:01 -07:00
printk trivial printk changes for 6.11 2024-07-25 13:18:41 -07:00
rcu Merge branches 'doc.2024.06.06a', 'fixes.2024.07.04a', 'mb.2024.06.28a', 'nocb.2024.06.03a', 'rcu-tasks.2024.06.06a', 'rcutorture.2024.06.06a' and 'srcu.2024.06.18a' into HEAD 2024-07-04 13:54:17 -07:00
sched hrtimer: Use and report correct timerslack values for realtime tasks 2024-08-23 20:13:02 +02:00
time timers: Annotate possible non critical data race of next_expiry 2024-09-04 11:57:56 +02:00
trace sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
.gitignore
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Kconfig.freezer
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Kconfig.hz
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Kconfig.kexec crash: clean up kdump related config items 2024-02-23 17:48:22 -08:00
Kconfig.locks
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Kconfig.preempt
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Makefile crash: split crash dumping code out from kexec_core.c 2024-02-23 17:48:22 -08:00
acct.c kernel misc: Remove the now superfluous sentinel elements from ctl_table array 2024-04-24 09:43:53 +02:00
async.c async: Use a dedicated unbound workqueue with raised min_active 2024-02-09 11:13:59 -10:00
audit.c audit: use KMEM_CACHE() instead of kmem_cache_create() 2024-01-25 10:12:22 -05:00
audit.h
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audit_fsnotify.c
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audit_tree.c fsnotify: create a wrapper fsnotify_find_inode_mark() 2024-04-04 16:24:16 +02:00
audit_watch.c fsnotify: create a wrapper fsnotify_find_inode_mark() 2024-04-04 16:24:16 +02:00
auditfilter.c ima: Avoid blocking in RCU read-side critical section 2024-06-13 14:26:50 -04:00
auditsc.c audit,io_uring: io_uring openat triggers audit reference count underflow 2023-10-13 18:34:46 +02:00
backtracetest.c backtracetest: add MODULE_DESCRIPTION() 2024-06-24 22:24:55 -07:00
bounds.c bounds: Use the right number of bits for power-of-two CONFIG_NR_CPUS 2024-04-29 08:29:29 -07:00
capability.c
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cfi.c
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compat.c
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configs.c
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context_tracking.c context_tracking: Make context_tracking_key __ro_after_init 2024-03-22 11:18:18 +01:00
cpu.c - Unrelated x86/cc changes queued here to avoid ugly cross-merges and 2024-07-15 19:36:01 -07:00
cpu_pm.c
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crash_core.c Mainly singleton patches, documented in their respective changelogs. 2024-05-19 14:02:03 -07:00
crash_reserve.c crash: remove header files which are included more than once 2024-06-24 22:25:08 -07:00
cred.c cred: Use KMEM_CACHE() instead of kmem_cache_create() 2024-02-23 17:33:31 -05:00
delayacct.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
dma.c
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elfcorehdr.c crash: remove dependency of FA_DUMP on CRASH_DUMP 2024-02-23 17:48:22 -08:00
exec_domain.c
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exit.c - 875fa64577da ("mm/hugetlb_vmemmap: fix race with speculative PFN 2024-07-21 17:15:46 -07:00
exit.h exit: add internal include file with helpers 2023-09-21 12:03:50 -06:00
extable.c
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fail_function.c
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fork.c posix-timers: Convert timer list to hlist 2024-07-29 21:57:35 +02:00
freezer.c Linux 6.7-rc6 2023-12-23 15:52:13 +01:00
gen_kheaders.sh kheaders: use `command -v` to test for existence of `cpio` 2024-05-30 01:13:20 +09:00
groups.c groups: Convert group_info.usage to refcount_t 2023-09-29 11:28:39 -07:00
hung_task.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
iomem.c
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irq_work.c
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jump_label.c jump_label: Simplify and clarify static_key_fast_inc_cpus_locked() 2024-06-11 11:25:24 +02:00
kallsyms.c kallsyms: get rid of code for absolute kallsyms 2024-07-20 16:33:21 +09:00
kallsyms_internal.h kallsyms: get rid of code for absolute kallsyms 2024-07-20 16:33:21 +09:00
kallsyms_selftest.c mm: vmalloc: enable memory allocation profiling 2024-04-25 20:55:57 -07:00
kallsyms_selftest.h
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kcmp.c file: convert to SLAB_TYPESAFE_BY_RCU 2023-10-19 11:02:48 +02:00
kcov.c kcov: don't lose track of remote references during softirqs 2024-06-15 10:43:08 -07:00
kexec.c crash: add a new kexec flag for hotplug support 2024-04-23 14:59:01 +10:00
kexec_core.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
kexec_elf.c
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kexec_file.c crash: add a new kexec flag for hotplug support 2024-04-23 14:59:01 +10:00
kexec_internal.h crash: remove dependency of FA_DUMP on CRASH_DUMP 2024-02-23 17:48:22 -08:00
kheaders.c
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kprobes.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
ksyms_common.c
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ksysfs.c vmlinux: Avoid weak reference to notes section 2024-05-02 19:48:26 +09:00
kthread.c kunit: Handle test faults 2024-05-06 14:22:02 -06:00
latencytop.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
module_signature.c
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notifier.c
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nsproxy.c pidfd: add pidfs 2024-03-01 12:23:37 +01:00
numa.c kernel/numa.c: Move logging out of numa.h 2023-12-20 19:26:30 -05:00
padata.c padata: Disable BH when taking works lock on MT path 2024-04-12 15:07:51 +08:00
panic.c kernel/panic: add verbose logging of kernel taints in backtraces 2024-06-24 22:25:05 -07:00
params.c params: Fix multi-line comment style 2023-12-01 09:51:44 -08:00
pid.c pidfs: remove config option 2024-03-13 12:53:53 -07:00
pid_namespace.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
pid_sysctl.h sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
profile.c profiling: Remove create_prof_cpu_mask(). 2024-04-27 11:17:48 -07:00
ptrace.c ptrace_attach: shift send(SIGSTOP) into ptrace_set_stopped() 2024-02-22 15:38:52 -08:00
range.c
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reboot.c kernel misc: Remove the now superfluous sentinel elements from ctl_table array 2024-04-24 09:43:53 +02:00
regset.c regset: use kvzalloc() for regset_get_alloc() 2024-04-25 21:07:03 -07:00
relay.c kernel: relay: remove relay_file_splice_read dead code, doesn't work 2023-12-29 12:22:27 -08:00
resource.c resource: Export find_resource_space() 2024-05-28 11:14:14 -05:00
resource_kunit.c resource: add missing MODULE_DESCRIPTION() 2024-06-28 19:36:30 -07:00
rseq.c
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scftorture.c scftorture: Make torture_type static 2024-05-30 15:31:51 -07:00
scs.c
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seccomp.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
signal.c signal: Replace BUG_ON()s 2024-07-29 21:57:35 +02:00
smp.c smp: Add missing destroy_work_on_stack() call in smp_call_on_cpu() 2024-07-10 22:40:39 +02:00
smpboot.c kthread: add kthread_stop_put 2023-10-04 10:41:57 -07:00
smpboot.h
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softirq.c softirq: Fix suspicious RCU usage in __do_softirq() 2024-04-29 05:03:51 +02:00
stackleak.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
stacktrace.c stacktrace: fix kernel-doc typo 2023-12-29 12:22:29 -08:00
static_call.c
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static_call_inline.c
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stop_machine.c
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sys.c hrtimer: Use and report correct timerslack values for realtime tasks 2024-08-23 20:13:02 +02:00
sys_ni.c Probes updates for v6.11: 2024-07-18 12:19:20 -07:00
sysctl-test.c sysctl: Add module description to sysctl-testing 2024-06-03 15:20:37 +02:00
sysctl.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
task_work.c task_work: Add TWA_NMI_CURRENT as an additional notify mode. 2024-07-09 13:26:34 +02:00
taskstats.c taskstats: fill_stats_for_tgid: use for_each_thread() 2023-10-04 10:41:57 -07:00
torture.c torture: Add MODULE_DESCRIPTION() 2024-05-30 15:31:38 -07:00
tracepoint.c
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tsacct.c tsacct: replace strncpy() with strscpy() 2024-07-12 16:39:53 -07:00
ucount.c sysctl changes for v6.10-rc1 2024-05-17 17:31:24 -07:00
uid16.c
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uid16.h
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umh.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
up.c smp: Change function signatures to use call_single_data_t 2023-09-13 14:59:24 +02:00
user-return-notifier.c
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user.c printk: Change type of CONFIG_BASE_SMALL to bool 2024-05-06 17:39:09 +02:00
user_namespace.c user_namespace: remove unnecessary NULL values from kbuf 2024-02-22 15:38:52 -08:00
usermode_driver.c
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utsname.c
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utsname_sysctl.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
vhost_task.c vhost_task: Handle SIGKILL by flushing work and exiting 2024-05-22 08:31:15 -04:00
vmcore_info.c kallsyms: get rid of code for absolute kallsyms 2024-07-20 16:33:21 +09:00
watch_queue.c watch_queue: fix kcalloc() arguments order 2023-12-21 13:17:54 +01:00
watchdog.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
watchdog_buddy.c
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watchdog_perf.c watchdog/perf: properly initialize the turbo mode timestamp and rearm counter 2024-07-17 21:11:34 -07:00
workqueue.c workqueue: Remove unneeded lockdep_assert_cpus_held() 2024-07-15 14:01:14 -10:00
workqueue_internal.h
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