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author | Ming Lei <ming.lei@redhat.com> | 2021-08-11 17:26:24 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-09-12 09:58:27 +0300 |
commit | ceffaa61b5bb5296e07cb7f4f494377eb659058f (patch) | |
tree | c1ed3e8a344acc0697fc2d9d22e51cd7675dd81a /init/do_mounts.h | |
parent | bc1b5c5f3e3bba6ab1cb1520871b71f0178eb550 (diff) | |
download | linux-ceffaa61b5bb5296e07cb7f4f494377eb659058f.tar.xz |
blk-mq: fix kernel panic during iterating over flush request
commit c2da19ed50554ce52ecbad3655c98371fe58599f upstream.
For fixing use-after-free during iterating over requests, we grabbed
request's refcount before calling ->fn in commit 2e315dc07df0 ("blk-mq:
grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter").
Turns out this way may cause kernel panic when iterating over one flush
request:
1) old flush request's tag is just released, and this tag is reused by
one new request, but ->rqs[] isn't updated yet
2) the flush request can be re-used for submitting one new flush command,
so blk_rq_init() is called at the same time
3) meantime blk_mq_queue_tag_busy_iter() is called, and old flush request
is retrieved from ->rqs[tag]; when blk_mq_put_rq_ref() is called,
flush_rq->end_io may not be updated yet, so NULL pointer dereference
is triggered in blk_mq_put_rq_ref().
Fix the issue by calling refcount_set(&flush_rq->ref, 1) after
flush_rq->end_io is set. So far the only other caller of blk_rq_init() is
scsi_ioctl_reset() in which the request doesn't enter block IO stack and
the request reference count isn't used, so the change is safe.
Fixes: 2e315dc07df0 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
Reported-by: "Blank-Burian, Markus, Dr." <blankburian@uni-muenster.de>
Tested-by: "Blank-Burian, Markus, Dr." <blankburian@uni-muenster.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20210811142624.618598-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Cc: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'init/do_mounts.h')
0 files changed, 0 insertions, 0 deletions