path: root/block/blk-lib.c
diff options
authorMike Snitzer <snitzer@redhat.com>2011-07-06 21:30:50 +0200
committerJens Axboe <jaxboe@fusionio.com>2011-07-06 21:32:02 +0200
commit0f79960391a5a1e3679956024e18aeeb0369ac44 (patch)
tree4b7e1f7a2b24f3307259024a5f29dbdc0f8b7bd2 /block/blk-lib.c
parent390192b300570b2bc721d77067ca133f58015ae8 (diff)
block: eliminate potential for infinite loop in blkdev_issue_discard
Due to the recently identified overflow in read_capacity_16() it was possible for max_discard_sectors to be zero but still have discards enabled on the associated device's queue. Eliminate the possibility for blkdev_issue_discard to infinitely loop. Interestingly this issue wasn't identified until a device, whose discard_granularity was 0 due to read_capacity_16 overflow, was consumed by blk_stack_limits() to construct limits for a higher-level DM multipath device. The multipath device's resulting limits never had the discard limits stacked because blk_stack_limits() will only do so if the bottom device's discard_granularity != 0. This resulted in the multipath device's limits.max_discard_sectors being 0. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block/blk-lib.c')
1 files changed, 4 insertions, 1 deletions
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 78e627e2581..64974b1c7cc 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -59,7 +59,10 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
* granularity
max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
- if (q->limits.discard_granularity) {
+ if (!unlikely(!max_discard_sectors)) {
+ /* Avoid infinite loop below. Being cautious never hurts. */
+ return -EOPNOTSUPP;
+ } else if (q->limits.discard_granularity) {
unsigned int disc_sects = q->limits.discard_granularity >> 9;
max_discard_sectors &= ~(disc_sects - 1);