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| author | Paolo Valente <paolo.valente@linaro.org> | 2021-10-15 16:43:36 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-10-17 07:03:02 -0600 |
| commit | d29bd41428cfff9b582c248db14a47e2be8457a8 (patch) | |
| tree | e2521992d6dc6c00eec13749946d4ccdf5d00abc /block/bfq-cgroup.c | |
| parent | a20417611b98e12a724e5c828c472ea16990b71f (diff) | |
| download | lwn-d29bd41428cfff9b582c248db14a47e2be8457a8.tar.gz lwn-d29bd41428cfff9b582c248db14a47e2be8457a8.zip | |
block, bfq: reset last_bfqq_created on group change
Since commit 430a67f9d616 ("block, bfq: merge bursts of newly-created
queues"), BFQ maintains a per-group pointer to the last bfq_queue
created. If such a queue, say bfqq, happens to move to a different
group, then bfqq is no more a valid last bfq_queue created for its
previous group. That pointer must then be cleared. Not resetting such
a pointer may also cause UAF, if bfqq happens to also be freed after
being moved to a different group. This commit performs this missing
reset. As such it fixes commit 430a67f9d616 ("block, bfq: merge bursts
of newly-created queues").
Such a missing reset is most likely the cause of the crash reported in [1].
With some analysis, we found that this crash was due to the
above UAF. And such UAF did go away with this commit applied [1].
Anyway, before this commit, that crash happened to be triggered in
conjunction with commit 2d52c58b9c9b ("block, bfq: honor already-setup
queue merges"). The latter was then reverted by commit ebc69e897e17
("Revert "block, bfq: honor already-setup queue merges""). Yet commit
2d52c58b9c9b ("block, bfq: honor already-setup queue merges") contains
no error related with the above UAF, and can then be restored.
[1] https://bugzilla.kernel.org/show_bug.cgi?id=214503
Fixes: 430a67f9d616 ("block, bfq: merge bursts of newly-created queues")
Tested-by: Grzegorz Kowal <custos.mentis@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20211015144336.45894-2-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-cgroup.c')
| -rw-r--r-- | block/bfq-cgroup.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index e2f14508f2d6..85b8e1c3a762 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -666,6 +666,12 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, bfq_put_idle_entity(bfq_entity_service_tree(entity), entity); bfqg_and_blkg_put(bfqq_group(bfqq)); + if (entity->parent && + entity->parent->last_bfqq_created == bfqq) + entity->parent->last_bfqq_created = NULL; + else if (bfqd->last_bfqq_created == bfqq) + bfqd->last_bfqq_created = NULL; + entity->parent = bfqg->my_entity; entity->sched_data = &bfqg->sched_data; /* pin down bfqg and its associated blkg */ |