diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2024-10-01 10:42:03 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-10-29 11:43:18 +0100 |
| commit | 4febce44cfebcb490b196d5d10ae9f403ca4c956 (patch) | |
| tree | a1ac7f9b10ba6c4e62b24bf21350aedc16f81f76 /kernel/signal.c | |
| parent | a76e1bbe879cf39952ec4b43ed653b0905635f24 (diff) | |
posix-timers: Cure si_sys_private race
The si_sys_private member of the siginfo which is embedded in the
preallocated sigqueue is used by the posix timer code to decide whether a
timer must be reprogrammed on signal delivery.
The handling of this is racy as a long standing comment in that code
documents. It is modified with the timer lock held, but without sighand
lock being held. The actual signal delivery code checks for it under
sighand lock without holding the timer lock.
Hand the new value to send_sigqueue() as argument and store it with sighand
lock held. This is an intermediate change to address this issue.
The arguments to this function will be cleanup in subsequent changes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.434338954@linutronix.de
Diffstat (limited to 'kernel/signal.c')
| -rw-r--r-- | kernel/signal.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index f420c430b24a..1563c83ff224 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1919,7 +1919,7 @@ void sigqueue_free(struct sigqueue *q) __sigqueue_free(q); } -int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type) +int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type, int si_private) { int sig = q->info.si_signo; struct sigpending *pending; @@ -1954,6 +1954,14 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type) if (!likely(lock_task_sighand(t, &flags))) goto ret; + /* + * Update @q::info::si_sys_private for posix timer signals with + * sighand locked to prevent a race against dequeue_signal() which + * decides based on si_sys_private whether to invoke + * posixtimer_rearm() or not. + */ + q->info.si_sys_private = si_private; + ret = 1; /* the signal is ignored */ result = TRACE_SIGNAL_IGNORED; if (!prepare_signal(sig, t, false)) |