Thomas Gleixner 8ce8849dd1 posix-timers: Ensure timer ID search-loop limit is valid ... posix_timer_add() tries to allocate a posix timer ID by starting from the cached ID which was stored by the last successful allocation. This is done in a loop searching the ID space for a free slot one by one. The loop has to terminate when the search wrapped around to the starting point. But that's racy vs. establishing the starting point. That is read out lockless, which leads to the following problem: CPU0 CPU1 posix_timer_add() start = sig->posix_timer_id; lock(hash_lock); ... posix_timer_add() if (++sig->posix_timer_id < 0) start = sig->posix_timer_id; sig->posix_timer_id = 0; So CPU1 can observe a negative start value, i.e. -1, and the loop break never happens because the condition can never be true: if (sig->posix_timer_id == start) break; While this is unlikely to ever turn into an endless loop as the ID space is huge (INT_MAX), the racy read of the start value caught the attention of KCSAN and Dmitry unearthed that incorrectness. Rewrite it so that all id operations are under the hash lock. Reported-by: syzbot+5c54bd3eb218bb595aa9@syzkaller.appspotmail.com Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/87bkhzdn6g.ffs@tglx		2023-06-18 22:41:48 +02:00
..
affinity.h
autogroup.h
clock.h
cond_resched.h
coredump.h	mm: add new api to enable ksm per process	2023-04-21 14:52:03 -07:00
cpufreq.h
cputime.h
deadline.h
debug.h
hotplug.h
idle.h
init.h
isolation.h	sched/isolation: add cpu_is_isolated() API	2023-04-18 16:29:43 -07:00
jobctl.h
loadavg.h
mm.h	IOMMU Updates for Linux 6.4	2023-04-30 13:00:38 -07:00
nohz.h
numa_balancing.h
posix-timers.h
prio.h
rseq_api.h
rt.h
sd_flags.h
signal.h	posix-timers: Ensure timer ID search-loop limit is valid	2023-06-18 22:41:48 +02:00
smt.h
stat.h
sysctl.h
task.h
task_flags.h
task_stack.h	sched: Fix KCSAN noinstr violation	2023-04-14 16:08:26 +02:00
thread_info_api.h
topology.h
types.h
user.h
vhost_task.h
wake_q.h
xacct.h