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| author | Yu Kuai <yukuai3@huawei.com> | 2024-09-09 21:41:48 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2024-09-10 16:32:09 -0600 |
| commit | 1ba0403ac6447f2d63914fb760c44a3b19c44eaf (patch) | |
| tree | d9d4c82ad7fb1b227949d2c76fcb893d94c0122b /block | |
| parent | 29390bb5661d49d10424ad8e915230de1f7074c9 (diff) | |
| download | lwn-1ba0403ac6447f2d63914fb760c44a3b19c44eaf.tar.gz lwn-1ba0403ac6447f2d63914fb760c44a3b19c44eaf.zip | |
block, bfq: fix uaf for accessing waker_bfqq after splitting
After commit 42c306ed7233 ("block, bfq: don't break merge chain in
bfq_split_bfqq()"), if the current procress is the last holder of bfqq,
the bfqq can be freed after bfq_split_bfqq(). Hence recored the bfqq and
then access bfqq->waker_bfqq may trigger UAF. What's more, the waker_bfqq
may in the merge chain of bfqq, hence just recored waker_bfqq is still
not safe.
Fix the problem by adding a helper bfq_waker_bfqq() to check if
bfqq->waker_bfqq is in the merge chain, and current procress is the only
holder.
Fixes: 42c306ed7233 ("block, bfq: don't break merge chain in bfq_split_bfqq()")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240909134154.954924-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/bfq-iosched.c | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index d1bf2b8a3576..d5d39974c674 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -6825,6 +6825,31 @@ static void bfq_prepare_request(struct request *rq) rq->elv.priv[0] = rq->elv.priv[1] = NULL; } +static struct bfq_queue *bfq_waker_bfqq(struct bfq_queue *bfqq) +{ + struct bfq_queue *new_bfqq = bfqq->new_bfqq; + struct bfq_queue *waker_bfqq = bfqq->waker_bfqq; + + if (!waker_bfqq) + return NULL; + + while (new_bfqq) { + if (new_bfqq == waker_bfqq) { + /* + * If waker_bfqq is in the merge chain, and current + * is the only procress. + */ + if (bfqq_process_refs(waker_bfqq) == 1) + return NULL; + break; + } + + new_bfqq = new_bfqq->new_bfqq; + } + + return waker_bfqq; +} + /* * If needed, init rq, allocate bfq data structures associated with * rq, and increment reference counters in the destination bfq_queue @@ -6886,7 +6911,7 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) /* If the queue was seeky for too long, break it apart. */ if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq) && !bic->bfqq_data[a_idx].stably_merged) { - struct bfq_queue *old_bfqq = bfqq; + struct bfq_queue *waker_bfqq = bfq_waker_bfqq(bfqq); /* Update bic before losing reference to bfqq */ if (bfq_bfqq_in_large_burst(bfqq)) @@ -6906,7 +6931,7 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) bfqq_already_existing = true; if (!bfqq_already_existing) { - bfqq->waker_bfqq = old_bfqq->waker_bfqq; + bfqq->waker_bfqq = waker_bfqq; bfqq->tentative_waker_bfqq = NULL; /* @@ -6916,7 +6941,7 @@ static struct bfq_queue *bfq_init_rq(struct request *rq) * woken_list of the waker. See * bfq_check_waker for details. */ - if (bfqq->waker_bfqq) + if (waker_bfqq) hlist_add_head(&bfqq->woken_list_node, &bfqq->waker_bfqq->woken_list); } |