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author | Mike Snitzer <snitzer@kernel.org> | 2022-07-20 20:58:04 +0300 |
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committer | Mike Snitzer <snitzer@kernel.org> | 2022-07-29 00:36:30 +0300 |
commit | 9dd1cd3220eca534f2d47afad7ce85f4c40118d8 (patch) | |
tree | eb4a62bec57415ffc4a735e7683ec5d7f77c3be1 /include/linux/dm-bufio.h | |
parent | 7dad24db59d2d2803576f2e3645728866a056dab (diff) | |
download | linux-9dd1cd3220eca534f2d47afad7ce85f4c40118d8.tar.xz |
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 <snitzer@kernel.org>
Diffstat (limited to 'include/linux/dm-bufio.h')
0 files changed, 0 insertions, 0 deletions