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| author | Joe Thornber <ejt@redhat.com> | 2015-05-29 16:52:51 +0300 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-05-29 20:41:16 +0300 |
| commit | 1c220c69ce0dcc0f234a9f263ad9c0864f971852 (patch) | |
| tree | 8ab6d754a212bd1fbfad8909686bc893cb889a82 | |
| parent | 15b94a690470038aa08247eedbebbe7e2218d5ee (diff) | |
| download | linux-1c220c69ce0dcc0f234a9f263ad9c0864f971852.tar.xz | |
dm: fix casting bug in dm_merge_bvec()
dm_merge_bvec() was originally added in f6fccb ("dm: introduce
merge_bvec_fn"). In that commit a value in sectors is converted to
bytes using << 9, and then assigned to an int. This code made
assumptions about the value of BIO_MAX_SECTORS.
A later commit 148e51 ("dm: improve documentation and code clarity in
dm_merge_bvec") was meant to have no functional change but it removed
the use of BIO_MAX_SECTORS in favor of using queue_max_sectors(). At
this point the cast from sector_t to int resulted in a zero value. The
fallout being dm_merge_bvec() would only allow a single page to be added
to a bio.
This interim fix is minimal for the benefit of stable@ because the more
comprehensive cleanup of passing a sector_t to all DM targets' merge
function will impact quite a few DM targets.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.19+
| -rw-r--r-- | drivers/md/dm.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index e24069aaeb18..2caf492890d6 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1723,8 +1723,7 @@ static int dm_merge_bvec(struct request_queue *q, struct mapped_device *md = q->queuedata; struct dm_table *map = dm_get_live_table_fast(md); struct dm_target *ti; - sector_t max_sectors; - int max_size = 0; + sector_t max_sectors, max_size = 0; if (unlikely(!map)) goto out; @@ -1739,8 +1738,16 @@ static int dm_merge_bvec(struct request_queue *q, max_sectors = min(max_io_len(bvm->bi_sector, ti), (sector_t) queue_max_sectors(q)); max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size; - if (unlikely(max_size < 0)) /* this shouldn't _ever_ happen */ - max_size = 0; + + /* + * FIXME: this stop-gap fix _must_ be cleaned up (by passing a sector_t + * to the targets' merge function since it holds sectors not bytes). + * Just doing this as an interim fix for stable@ because the more + * comprehensive cleanup of switching to sector_t will impact every + * DM target that implements a ->merge hook. + */ + if (max_size > INT_MAX) + max_size = INT_MAX; /* * merge_bvec_fn() returns number of bytes @@ -1748,7 +1755,7 @@ static int dm_merge_bvec(struct request_queue *q, * max is precomputed maximal io size */ if (max_size && ti->type->merge) - max_size = ti->type->merge(ti, bvm, biovec, max_size); + max_size = ti->type->merge(ti, bvm, biovec, (int) max_size); /* * If the target doesn't support merge method and some of the devices * provided their merge_bvec method (we know this by looking for the |