From 5be28c8f85ce99ed2d329d2ad8bdd18ea19473a5 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 19 Mar 2021 19:25:13 -0600 Subject: signal: don't allow sending any signals to PF_IO_WORKER threads They don't take signals individually, and even if they share signals with the parent task, don't allow them to be delivered through the worker thread. Linux does allow this kind of behavior for regular threads, but it's really a compatability thing that we need not care about for the IO threads. Reported-by: Stefan Metzmacher Signed-off-by: Jens Axboe --- kernel/signal.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index ba4d1ef39a9e..11cabcf20e7a 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -833,6 +833,9 @@ static int check_kill_permission(int sig, struct kernel_siginfo *info, if (!valid_signal(sig)) return -EINVAL; + /* PF_IO_WORKER threads don't take any signals */ + if (t->flags & PF_IO_WORKER) + return -ESRCH; if (!si_fromuser(info)) return 0; -- cgit v1.2.3 From 4db4b1a0d1779dc159f7b87feb97030ec0b12597 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sun, 21 Mar 2021 09:37:48 -0600 Subject: signal: don't allow STOP on PF_IO_WORKER threads Just like we don't allow normal signals to IO threads, don't deliver a STOP to a task that has PF_IO_WORKER set. The IO threads don't take signals in general, and have no means of flushing out a stop either. Longer term, we may want to look into allowing stop of these threads, as it relates to eg process freezing. For now, this prevents a spin issue if a SIGSTOP is delivered to the parent task. Reported-by: Stefan Metzmacher Signed-off-by: Jens Axboe Signed-off-by: "Eric W. Biederman" --- kernel/signal.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 11cabcf20e7a..f2a1b898da29 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -288,7 +288,8 @@ bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask) JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING)); BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK)); - if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING))) + if (unlikely(fatal_signal_pending(task) || + (task->flags & (PF_EXITING | PF_IO_WORKER)))) return false; if (mask & JOBCTL_STOP_SIGMASK) -- cgit v1.2.3