This is a note to let you know that I've just added the patch titled
dm: fix dm-raid crash if md_handle_request() splits bio
to the 5.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-fix-dm-raid-crash-if-md_handle_request-splits-bio.patch
and it can be found in the queue-5.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 033448c1277b287ae1beffc7fe311fcda224825b
Author: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Wed Jul 20 13:58:04 2022 -0400
dm: fix dm-raid crash if md_handle_request() splits bio
[ Upstream commit 9dd1cd3220eca534f2d47afad7ce85f4c40118d8 ]
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@xxxxxxxxxxxxxxx
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index a55fc28d2a29..ba3638d1d046 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3097,6 +3097,7 @@ 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 2b75f1ef7386..36c704b50ac3 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -578,9 +578,6 @@ 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);
@@ -614,6 +611,7 @@ 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;
@@ -623,14 +621,10 @@ 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;
@@ -646,6 +640,11 @@ 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 47a01c7cffdf..e9c043f12e53 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 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 */
