[dm-devel] [PATCH 3/4] dm clone: Add missing casts to prevent overflows and data corruption

[Nikos Tsironis]

Add missing casts when converting from regions to sectors.

In case BITS_PER_LONG == 32, the lack of the appropriate casts can lead
to overflows and miscalculation of the device sector.

As a result, we could end up discarding and/or copying the wrong parts
of the device, thus corrupting the device's data.

Fixes: 7431b7835f55 ("dm: add clone target")
Cc: stable at vger.kernel.org # v5.4+
Signed-off-by: Nikos Tsironis <ntsironis at arrikto.com>
---
 drivers/md/dm-clone-target.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-clone-target.c b/drivers/md/dm-clone-target.c
index 6ee85fb3388a..ca5020c58f7c 100644
--- a/drivers/md/dm-clone-target.c
+++ b/drivers/md/dm-clone-target.c
@@ -282,7 +282,7 @@ static bool bio_triggers_commit(struct clone *clone, struct bio *bio)
 /* Get the address of the region in sectors */
 static inline sector_t region_to_sector(struct clone *clone, unsigned long region_nr)
 {
-	return (region_nr << clone->region_shift);
+	return ((sector_t)region_nr << clone->region_shift);
 }
 
 /* Get the region number of the bio */
@@ -471,7 +471,7 @@ static void complete_discard_bio(struct clone *clone, struct bio *bio, bool succ
 	if (test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags) && success) {
 		remap_to_dest(clone, bio);
 		bio_region_range(clone, bio, &rs, &nr_regions);
-		trim_bio(bio, rs << clone->region_shift,
+		trim_bio(bio, region_to_sector(clone, rs),
 			 nr_regions << clone->region_shift);
 		generic_make_request(bio);
 	} else
@@ -804,11 +804,14 @@ static void hydration_copy(struct dm_clone_region_hydration *hd, unsigned int nr
 	struct dm_io_region from, to;
 	struct clone *clone = hd->clone;
 
+	if (WARN_ON(!nr_regions))
+		return;
+
 	region_size = clone->region_size;
 	region_start = hd->region_nr;
 	region_end = region_start + nr_regions - 1;
 
-	total_size = (nr_regions - 1) << clone->region_shift;
+	total_size = region_to_sector(clone, nr_regions - 1);
 
 	if (region_end == clone->nr_regions - 1) {
 		/*
-- 
2.11.0