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

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Date:   Fri, 28 Dec 2018 12:52:39 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mikulas Patocka <mpatocka@...hat.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 02/22] block: fix infinite loop if the device loses discard capability

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ 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@...hat.com>
Tested-by: Zdenek Kabelac <mpatocka@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.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