From 9dd1cd3220eca534f2d47afad7ce85f4c40118d8 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 20 Jul 2022 13:58:04 -0400 Subject: [PATCH] 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 --- drivers/md/dm-raid.c | 1 + drivers/md/dm.c | 13 ++++++------- include/linux/device-mapper.h | 6 ++++++ include/uapi/linux/dm-ioctl.h | 4 ++-- 4 files changed, 15 insertions(+), 9 deletions(-) diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c index e6a9b8c..3203aec 100644 --- a/drivers/md/dm-raid.c +++ b/drivers/md/dm-raid.c @@ -3095,6 +3095,7 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv) INIT_WORK(&rs->md.event_work, do_table_event); ti->private = rs; ti->num_flush_bios = 1; + ti->needs_bio_set_dev = true; /* Restore any requested new layout for conversion decision */ rs_config_restore(rs, &rs_layout); diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 47bcc50..f6a6437 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -574,9 +574,6 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio) struct bio *clone; clone = bio_alloc_clone(NULL, bio, GFP_NOIO, &md->mempools->io_bs); - /* Set default bdev, but target must bio_set_dev() before issuing IO */ - clone->bi_bdev = md->disk->part0; - tio = clone_to_tio(clone); tio->flags = 0; dm_tio_set_flag(tio, DM_TIO_INSIDE_DM_IO); @@ -609,6 +606,7 @@ static void free_io(struct dm_io *io) static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti, unsigned target_bio_nr, unsigned *len, gfp_t gfp_mask) { + struct mapped_device *md = ci->io->md; struct dm_target_io *tio; struct bio *clone; @@ -618,14 +616,10 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti, /* alloc_io() already initialized embedded clone */ clone = &tio->clone; } else { - struct mapped_device *md = ci->io->md; - clone = bio_alloc_clone(NULL, ci->bio, gfp_mask, &md->mempools->bs); if (!clone) return NULL; - /* Set default bdev, but target must bio_set_dev() before issuing IO */ - clone->bi_bdev = md->disk->part0; /* REQ_DM_POLL_LIST shouldn't be inherited */ clone->bi_opf &= ~REQ_DM_POLL_LIST; @@ -641,6 +635,11 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti, tio->len_ptr = len; tio->old_sector = 0; + /* Set default bdev, but target must bio_set_dev() before issuing IO */ + clone->bi_bdev = md->disk->part0; + if (unlikely(ti->needs_bio_set_dev)) + bio_set_dev(clone, md->disk->part0); + if (len) { clone->bi_iter.bi_size = to_bytes(*len); if (bio_integrity(clone)) diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 920085d..04c6acf 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -373,6 +373,12 @@ struct dm_target { * after returning DM_MAPIO_SUBMITTED from its map function. */ bool accounts_remapped_io:1; + + /* + * Set if the target will submit the DM bio without first calling + * bio_set_dev(). NOTE: ideally a target should _not_ need this. + */ + bool needs_bio_set_dev:1; }; void *dm_per_bio_data(struct bio *bio, size_t data_size); diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index 2e9550f..27ad9671 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 */ -- 2.7.4