drivers:md:fix a potential use-after-free bug

In line 2884, "raid5_release_stripe(sh);" drops the reference to sh and
may cause sh to be released. However, sh is subsequently used in lines
2886 "if (sh->batch_head && sh != sh->batch_head)". This may result in an
use-after-free bug.

It can be fixed by moving "raid5_release_stripe(sh);" to the bottom of
the function.

Signed-off-by: Wentao_Liang <Wentao_Liang_g@163.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 8d10b190bdbbe24088ecfa1bdadb2d5117958ce4..860c45c10a57d628b1b26328a7ee819dfdb189c7 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2952,10 +2952,10 @@ static void raid5_end_write_request(struct bio *bi)
        if (!test_and_clear_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags))
                clear_bit(R5_LOCKED, &sh->dev[i].flags);
        set_bit(STRIPE_HANDLE, &sh->state);
-       raid5_release_stripe(sh);
 
        if (sh->batch_head && sh != sh->batch_head)
                raid5_release_stripe(sh->batch_head);
+       raid5_release_stripe(sh);
 }
 
 static void raid5_error(struct mddev *mddev, struct md_rdev *rdev)