[PATCH 1/2] signal: don't allow sending any signals to PF_IO_WORKER threads

[Jens Axboe <axboe@kernel.dk>]

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.

Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 kernel/signal.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/signal.c b/kernel/signal.c
index ba4d1ef39a9e..730ecd3d6faf 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 -EPERM;
 
 	if (!si_fromuser(info))
 		return 0;
-- 
2.31.0