md/raid10: fix bug when raid10 recovery fails to recover a block.

commit e875ecea266a543e643b19e44cf472f1412708f9
    md/raid10 record bad blocks as needed during recovery.

added code to the "cannot recover this block" path to record a bad
block rather than fail the whole recovery.
Unfortunately this new case was placed *after* r10bio was freed rather
than *before*, yet it still uses r10bio.
This is will crash with a null dereference.

So move the freeing of r10bio down where it is safe.

Cc: stable@vger.kernel.org (v3.1+)
Fixes: e875ecea266a543e643b19e44cf472f1412708f9
Reported-by: Damian Nowak <spam@nowaker.net>
URL: https://bugzilla.kernel.org/show_bug.cgi?id=68181
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 6528521..06eeb99 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3218,10 +3218,6 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr,
                        if (j == conf->copies) {
                                /* Cannot recover, so abort the recovery or
                                 * record a bad block */
-                               put_buf(r10_bio);
-                               if (rb2)
-                                       atomic_dec(&rb2->remaining);
-                               r10_bio = rb2;
                                if (any_working) {
                                        /* problem is that there are bad blocks
                                         * on other device(s)
@@ -3253,6 +3249,10 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr,
                                        mirror->recovery_disabled
                                                = mddev->recovery_disabled;
                                }
+                               put_buf(r10_bio);
+                               if (rb2)
+                                       atomic_dec(&rb2->remaining);
+                               r10_bio = rb2;
                                break;
                        }
                }