linux-kernel - [PATCH 5.5 186/257] dm clone: Add missing casts to prevent overflows and data corruption

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Date:   Thu, 16 Apr 2020 15:23:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nikos Tsironis <ntsironis@...ikto.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 5.5 186/257] dm clone: Add missing casts to prevent overflows and data corruption

From: Nikos Tsironis <ntsironis@...ikto.com>

commit 9fc06ff56845cc5ccafec52f545fc2e08d22f849 upstream.

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@...r.kernel.org # v5.4+
Signed-off-by: Nikos Tsironis <ntsironis@...ikto.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-clone-target.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/md/dm-clone-target.c
+++ b/drivers/md/dm-clone-target.c
@@ -282,7 +282,7 @@ static bool bio_triggers_commit(struct c
 /* 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
 	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_clo
 	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) {
 		/*