From 83c10e8dd43628d0bf86486616556cd749a3c310 Mon Sep 17 00:00:00 2001 From: Matt Whitlock Date: Sun, 18 Jan 2026 13:36:15 -0500 Subject: [PATCH] dm-unstripe: fix mapping bug when there are multiple targets in a table The "unstriped" device-mapper target incorrectly calculates the sector offset on the mapped device when the target's origin is not zero. Take for example this hypothetical concatenation of the members of a two-disk RAID0: linearized: 0 2097152 unstriped 2 128 0 /dev/md/raid0 0 linearized: 2097152 2097152 unstriped 2 128 1 /dev/md/raid0 0 The intent in this example is to create a single device named /dev/mapper/linearized that comprises all of the chunks of the first disk of the RAID0 set, followed by all of the chunks of the second disk of the RAID0 set. This fails because dm-unstripe.c's map_to_core function does its computations based on the sector number within the mapper device rather than the sector number within the target. The bug turns invisible when the target's origin is at sector zero of the mapper device, as is the common case. In the example above, however, what happens is that the first half of the mapper device gets mapped correctly to the first disk of the RAID0, but the second half of the mapper device gets mapped past the end of the RAID0 device, and accesses to any of those sectors return errors. Signed-off-by: Matt Whitlock Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Fixes: 18a5bf270532 ("dm: add unstriped target") --- drivers/md/dm-unstripe.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/dm-unstripe.c b/drivers/md/dm-unstripe.c index e8a9432057dce..17be483595642 100644 --- a/drivers/md/dm-unstripe.c +++ b/drivers/md/dm-unstripe.c @@ -117,7 +117,7 @@ static void unstripe_dtr(struct dm_target *ti) static sector_t map_to_core(struct dm_target *ti, struct bio *bio) { struct unstripe_c *uc = ti->private; - sector_t sector = bio->bi_iter.bi_sector; + sector_t sector = dm_target_offset(ti, bio->bi_iter.bi_sector); sector_t tmp_sector = sector; /* Shift us up to the right "row" on the stripe */ -- 2.47.3