From: Oleg Nesterov oleg@redhat.com
stable inclusion from stable-v5.10.132 commit 91530f675e88c6b27306c35ca4e482fb956794d1 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5YS3T
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit d5b36a4dbd06c5e8e36ca8ccc552f679069e2946 upstream.
As Chris explains, the comment above exit_itimers() is not correct, we can race with proc_timers_seq_ops. Change exit_itimers() to clear signal->posix_timers with ->siglock held.
Cc: stable@vger.kernel.org Reported-by: chris@accessvector.net Signed-off-by: Oleg Nesterov oleg@redhat.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com
Conflicts: fs/exec.c
Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Acked-by: Xie XiuQi xiexiuqi@huawei.com --- fs/exec.c | 2 +- include/linux/sched/task.h | 2 +- kernel/exit.c | 2 +- kernel/time/posix-timers.c | 19 ++++++++++++++----- 4 files changed, 17 insertions(+), 8 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c index 97f991f79e69..add4a298a49a 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1277,7 +1277,7 @@ int begin_new_exec(struct linux_binprm * bprm) spin_lock_irq(&me->sighand->siglock); posix_cpu_timers_exit(me); spin_unlock_irq(&me->sighand->siglock); - exit_itimers(me->signal); + exit_itimers(me); flush_itimer_signals(); #endif
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index cea4bdfd0f05..df9505faed27 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -82,7 +82,7 @@ static inline void exit_thread(struct task_struct *tsk) extern void do_group_exit(int);
extern void exit_files(struct task_struct *); -extern void exit_itimers(struct signal_struct *); +extern void exit_itimers(struct task_struct *);
extern pid_t kernel_clone(struct kernel_clone_args *kargs); struct task_struct *fork_idle(int); diff --git a/kernel/exit.c b/kernel/exit.c index d13d67fc5f4e..ab900b661867 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -782,7 +782,7 @@ void __noreturn do_exit(long code)
#ifdef CONFIG_POSIX_TIMERS hrtimer_cancel(&tsk->signal->real_timer); - exit_itimers(tsk->signal); + exit_itimers(tsk); #endif if (tsk->mm) setmax_mm_hiwater_rss(&tsk->signal->maxrss, tsk->mm); diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 7363f81dc31a..c2a02f2bb623 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -1051,15 +1051,24 @@ static void itimer_delete(struct k_itimer *timer) }
/* - * This is called by do_exit or de_thread, only when there are no more - * references to the shared signal_struct. + * This is called by do_exit or de_thread, only when nobody else can + * modify the signal->posix_timers list. Yet we need sighand->siglock + * to prevent the race with /proc/pid/timers. */ -void exit_itimers(struct signal_struct *sig) +void exit_itimers(struct task_struct *tsk) { + struct list_head timers; struct k_itimer *tmr;
- while (!list_empty(&sig->posix_timers)) { - tmr = list_entry(sig->posix_timers.next, struct k_itimer, list); + if (list_empty(&tsk->signal->posix_timers)) + return; + + spin_lock_irq(&tsk->sighand->siglock); + list_replace_init(&tsk->signal->posix_timers, &timers); + spin_unlock_irq(&tsk->sighand->siglock); + + while (!list_empty(&timers)) { + tmr = list_first_entry(&timers, struct k_itimer, list); itimer_delete(tmr); } }