md/raid5: don't index beyond end of array in need_this_block().

When need_this_block probably shouldn't be called when there
are more than 2 failed devices, we really don't want it to try
indexing beyond the end of the failed_num[] of fdev[] arrays.

So limit the loops to at most 2 iterations.

Reported-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 2105e5f1fd314b724e3c6d5206ffaf9f8678fac4..d66ff723df458d8fe3a8c7586002b34df3b6b4c6 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3304,7 +3304,7 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
                 */
                return 0;
 
-       for (i = 0; i < s->failed; i++) {
+       for (i = 0; i < s->failed && i < 2; i++) {
                if (fdev[i]->towrite &&
                    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&
                    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
@@ -3328,7 +3328,7 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
            sh->sector < sh->raid_conf->mddev->recovery_cp)
                /* reconstruct-write isn't being forced */
                return 0;
-       for (i = 0; i < s->failed; i++) {
+       for (i = 0; i < s->failed && i < 2; i++) {
                if (s->failed_num[i] != sh->pd_idx &&
                    s->failed_num[i] != sh->qd_idx &&
                    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&