md: don't use flush_signals in userspace processes
The function flush_signals clears all pending signals for the process. It
may be used by kernel threads when we need to prepare a kernel thread for
responding to signals. However using this function for an userspaces
processes is incorrect - clearing signals without the program expecting it
can cause misbehavior.
The raid1 and raid5 code uses flush_signals in its request routine because
it wants to prepare for an interruptible wait. This patch drops
flush_signals and uses sigprocmask instead to block all signals (including
SIGKILL) around the schedule() call. The signals are not lost, but the
schedule() call won't respond to them.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index c71739b..7866563 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1334,7 +1334,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
*/
DEFINE_WAIT(w);
for (;;) {
- flush_signals(current);
+ sigset_t full, old;
prepare_to_wait(&conf->wait_barrier,
&w, TASK_INTERRUPTIBLE);
if (bio_end_sector(bio) <= mddev->suspend_lo ||
@@ -1344,7 +1344,10 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
bio->bi_iter.bi_sector,
bio_end_sector(bio))))
break;
+ sigfillset(&full);
+ sigprocmask(SIG_BLOCK, &full, &old);
schedule();
+ sigprocmask(SIG_SETMASK, &old, NULL);
}
finish_wait(&conf->wait_barrier, &w);
}