md: don't use flush_signals in userspace processes

commit f9c79bc05a2a91f4fba8bfd653579e066714b1ec upstream.

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>
Acked-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 7b75a19..308e8c8 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -875,13 +875,16 @@ static void make_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->bi_sector + bio->bi_size/512 <= mddev->suspend_lo ||
                            bio->bi_sector >= mddev->suspend_hi)
                                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 6056ee7..2682eb9 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3823,12 +3823,16 @@ static void 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)
+                                   logical_sector < mddev->suspend_hi) {
+                                       sigset_t full, old;
+                                       sigfillset(&full);
+                                       sigprocmask(SIG_BLOCK, &full, &old);
                                        schedule();
+                                       sigprocmask(SIG_SETMASK, &old, NULL);
+                               }
                                goto retry;
                        }