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 c71739b87ab73c48a13de23579a99714307f8fa3..7866563338fa48fb909dbfd9a5c7a6429c164458 100644 (file)
--- 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);
        }

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index b218a42fd7027ec1671bb5a33fb8fb92499c47dd..547d5fa45a42d475721df159c261911ca344be66 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -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;