On Wed, Jun 07 2017, Mikulas Patocka wrote:
> 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@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Thanks for catching that!
Acked-by: NeilBrown <neilb@xxxxxxxx>
NeilBrown
>
> ---
> drivers/md/raid1.c | 5 ++++-
> drivers/md/raid5.c | 5 ++++-
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> Index: linux-4.12-rc4/drivers/md/raid1.c
> ===================================================================
> --- linux-4.12-rc4.orig/drivers/md/raid1.c
> +++ linux-4.12-rc4/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);
> }
> Index: linux-4.12-rc4/drivers/md/raid5.c
> ===================================================================
> --- linux-4.12-rc4.orig/drivers/md/raid5.c
> +++ linux-4.12-rc4/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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