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authorYu Kuai <yukuai3@huawei.com>2023-03-08 05:32:08 +0300
committerJens Axboe <axboe@kernel.dk>2023-03-08 17:34:50 +0300
commite2f2a39452c43b64ea3191642a2661cb8d03827a (patch)
treebb85a3d9c05661e2c356f44fa95b0da4e059064d /block
parente33062213ff2f9151e0d125e1c00f524c2b7acfe (diff)
downloadlinux-e2f2a39452c43b64ea3191642a2661cb8d03827a.tar.xz
block, bfq: fix uaf for 'stable_merge_bfqq'
Before commit fd571df0ac5b ("block, bfq: turn bfqq_data into an array in bfq_io_cq"), process reference is read before bfq_put_stable_ref(), and it's safe if bfq_put_stable_ref() put the last reference, because process reference will be 0 and 'stable_merge_bfqq' won't be accessed in this case. However, the commit changed the order and will cause uaf for 'stable_merge_bfqq'. In order to emphasize that bfq_put_stable_ref() can drop the last reference, fix the problem by moving bfq_put_stable_ref() to the end of bfq_setup_stable_merge(). Fixes: fd571df0ac5b ("block, bfq: turn bfqq_data into an array in bfq_io_cq") Reported-and-tested-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com> Link: https://lore.kernel.org/linux-block/20230307071448.rzihxbm4jhbf5krj@shindev/ Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/bfq-iosched.c18
1 files changed, 9 insertions, 9 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 8a8d4441519c..d9ed3108c17a 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2854,11 +2854,11 @@ bfq_setup_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq,
{
int proc_ref = min(bfqq_process_refs(bfqq),
bfqq_process_refs(stable_merge_bfqq));
- struct bfq_queue *new_bfqq;
+ struct bfq_queue *new_bfqq = NULL;
- if (idling_boosts_thr_without_issues(bfqd, bfqq) ||
- proc_ref == 0)
- return NULL;
+ bfqq_data->stable_merge_bfqq = NULL;
+ if (idling_boosts_thr_without_issues(bfqd, bfqq) || proc_ref == 0)
+ goto out;
/* next function will take at least one ref */
new_bfqq = bfq_setup_merge(bfqq, stable_merge_bfqq);
@@ -2873,6 +2873,11 @@ bfq_setup_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq,
new_bfqq_data->stably_merged = true;
}
}
+
+out:
+ /* deschedule stable merge, because done or aborted here */
+ bfq_put_stable_ref(stable_merge_bfqq);
+
return new_bfqq;
}
@@ -2933,11 +2938,6 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_queue *stable_merge_bfqq =
bfqq_data->stable_merge_bfqq;
- /* deschedule stable merge, because done or aborted here */
- bfq_put_stable_ref(stable_merge_bfqq);
-
- bfqq_data->stable_merge_bfqq = NULL;
-
return bfq_setup_stable_merge(bfqd, bfqq,
stable_merge_bfqq,
bfqq_data);