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Subject[PATCH 4.12 075/196] md: dont use flush_signals in userspace processes
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mikulas Patocka <mpatocka@redhat.com>

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/raid1.c | 5 ++++-
drivers/md/raid5.c | 5 ++++-
2 files changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1335,7 +1335,7 @@ static void raid1_write_request(struct m
*/
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 ||
@@ -1345,7 +1345,10 @@ static void raid1_write_request(struct m
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);
}
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5693,12 +5693,15 @@ static void raid5_make_request(struct md
* 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;

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