CVE-2026-43278

In the Linux kernel, the following vulnerability has been resolved:

dm: clear cloned request bio pointer when last clone bio completes

Stale rq->bio values have been observed to cause double-initialization of

cloned bios in request-based device-mapper targets, leading to

use-after-free and double-free scenarios.

One such case occurs when using dm-multipath on top of a PCIe NVMe

namespace, where cloned request bios are freed during

blk_complete_request(), but rq->bio is left intact. Subsequent clone

teardown then attempts to free the same bios again via

blk_rq_unprep_clone().

The resulting double-free path looks like:

nvme_pci_complete_batch()

nvme_complete_batch()

blk_mq_end_request_batch()

blk_complete_request() // called on a DM clone request

bio_endio() // first free of all clone bios

...

rq->end_io() // end_clone_request()

dm_complete_request(tio->orig)

dm_softirq_done()

dm_done()

dm_end_request()

blk_rq_unprep_clone() // second free of clone bios

Fix this by clearing the clone request's bio pointer when the last cloned

bio completes, ensuring that later teardown paths do not attempt to free

already-released bios.