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md: don't use flush_signals in userspace processes

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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>
This commit is contained in:
Mikulas Patocka 2017-06-07 19:05:31 -04:00 committed by Shaohua Li
parent cc27b0c78c
commit f9c79bc05a
2 changed files with 8 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

5
drivers/md/raid1.c
View file

@ -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);
}

5
drivers/md/raid5.c
View file

@ -5693,12 +5693,15 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
* userspace, we want an interruptible
* wait.
*/
flush_signals(current);
prepare_to_wait(&conf->wait_for_overlap,
&w, TASK_INTERRUPTIBLE);
if (logical_sector >= mddev->suspend_lo &&
logical_sector < mddev->suspend_hi) {
sigset_t full, old;
sigfillset(&full);
sigprocmask(SIG_BLOCK, &full, &old);
schedule();
sigprocmask(SIG_SETMASK, &old, NULL);
do_prepare = true;
}
goto retry;