[PATCH 4.9 02/22] block: fix infinite loop if the device loses discard capability

Greg Kroah-Hartman
2018-12-28T12:17:49Z

[ Upstream commit b88aef36b87c9787a4db724923ec4f57dfd513f3 ]

If __blkdev_issue_discard is in progress and a device mapper device is
reloaded with a table that doesn't support discard,
q->limits.max_discard_sectors is set to zero. This results in infinite
loop in __blkdev_issue_discard.

This patch checks if max_discard_sectors is zero and aborts with
-EOPNOTSUPP.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Zdenek Kabelac <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-lib.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index d8b89c58af3d..af1d26f79878 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -69,6 +69,8 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
*/
req_sects = min_t(sector_t, nr_sects,
q->limits.max_discard_sectors);
+ if (!req_sects)
+ goto fail;
if (req_sects > UINT_MAX >> 9)
req_sects = UINT_MAX >> 9;

@@ -106,6 +108,14 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,

*biop = bio;
return 0;
+
+fail:
+ if (bio) {
+ submit_bio_wait(bio);
+ bio_put(bio);
+ }
+ *biop = NULL;
+ return -EOPNOTSUPP;
}
EXPORT_SYMBOL(__blkdev_issue_discard);

--
2.19.1