From 9dd1cd3220eca534f2d47afad7ce85f4c40118d8 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 20 Jul 2022 13:58:04 -0400 Subject: dm: fix dm-raid crash if md_handle_request() splits bio Commit ca522482e3eaf ("dm: pass NULL bdev to bio_alloc_clone") introduced the optimization to _not_ perform bio_associate_blkg()'s relatively costly work when DM core clones its bio. But in doing so it exposed the possibility for DM's cloned bio to alter DM target behavior (e.g. crash) if a target were to issue IO without first calling bio_set_dev(). The DM raid target can trigger an MD crash due to its need to split the DM bio that is passed to md_handle_request(). The split will recurse to submit_bio_noacct() using a bio with an uninitialized ->bi_blkg. This NULL bio->bi_blkg causes blk_throtl_bio() to dereference a NULL blkg_to_tg(bio->bi_blkg). Fix this in DM core by adding a new 'needs_bio_set_dev' target flag that will make alloc_tio() call bio_set_dev() on behalf of the target. dm-raid is the only target that requires this flag. bio_set_dev() initializes the DM cloned bio's ->bi_blkg, using bio_associate_blkg, before passing the bio to md_handle_request(). Long-term fix would be to audit and refactor MD code to rely on DM to split its bio, using dm_accept_partial_bio(), but there are MD raid personalities (e.g. raid1 and raid10) whose implementation are tightly coupled to handling the bio splitting inline. Fixes: ca522482e3eaf ("dm: pass NULL bdev to bio_alloc_clone") Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer --- include/uapi/linux/dm-ioctl.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index 2e9550fef90f..27ad9671f2df 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -286,9 +286,9 @@ enum { #define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl) #define DM_VERSION_MAJOR 4 -#define DM_VERSION_MINOR 46 +#define DM_VERSION_MINOR 47 #define DM_VERSION_PATCHLEVEL 0 -#define DM_VERSION_EXTRA "-ioctl (2022-02-22)" +#define DM_VERSION_EXTRA "-ioctl (2022-07-28)" /* Status bits */ #define DM_READONLY_FLAG (1 << 0) /* In/Out */ -- cgit v1.2.3-59-g8ed1b