diff options
authorDave Chinner <dchinner@redhat.com>2018-11-14 08:17:18 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-02-01 09:37:12 +0000
commitf387897cf5b8cad1313c683419f53cdbabc9f092 (patch)
parentb0be61a5a59e295dc0804afd13e51ae9aa846b69 (diff)
block: fix 32 bit overflow in __blkdev_issue_discard()
commit 4800bf7bc8c725e955fcbc6191cc872f43f506d3 upstream. A discard cleanup merged into 4.20-rc2 causes fstests xfs/259 to fall into an endless loop in the discard code. The test is creating a device that is exactly 2^32 sectors in size to test mkfs boundary conditions around the 32 bit sector overflow region. mkfs issues a discard for the entire device size by default, and hence this throws a sector count of 2^32 into blkdev_issue_discard(). It takes the number of sectors to discard as a sector_t - a 64 bit value. The commit ba5d73851e71 ("block: cleanup __blkdev_issue_discard") takes this sector count and casts it to a 32 bit value before comapring it against the maximum allowed discard size the device has. This truncates away the upper 32 bits, and so if the lower 32 bits of the sector count is zero, it starts issuing discards of length 0. This causes the code to fall into an endless loop, issuing a zero length discards over and over again on the same sector. Fixes: ba5d73851e71 ("block: cleanup __blkdev_issue_discard") Tested-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Dave Chinner <dchinner@redhat.com> Killed pointless WARN_ON(). Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 3 insertions, 1 deletions
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 41088d5466c1..0dbc9e2ab9a3 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -56,9 +56,11 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
return -EINVAL;
while (nr_sects) {
- unsigned int req_sects = min_t(unsigned int, nr_sects,
+ sector_t req_sects = min_t(sector_t, nr_sects,
+ WARN_ON_ONCE((req_sects << 9) > UINT_MAX);
bio = next_bio(bio, 0, gfp_mask);
bio->bi_iter.bi_sector = sector;
bio_set_dev(bio, bdev);