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    Subject[PATCH 4.4 40/83] md: dont use flush_signals in userspace processes
    Date
    4.4-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
    @@ -1088,7 +1088,7 @@ static void make_request(struct mddev *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 ||
    @@ -1097,7 +1097,10 @@ static void make_request(struct mddev *m
    !md_cluster_ops->area_resyncing(mddev, WRITE,
    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
    @@ -5279,12 +5279,15 @@ static void make_request(struct mddev *m
    * 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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