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io_uring: fix wqe->lock/completion_lock deadlock

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commit 907d1df30a51cc1a1d25414a00cde0494b83df7b upstream.

Joseph reports following deadlock:

CPU0:
...
io_kill_linked_timeout  // &ctx->completion_lock
io_commit_cqring
__io_queue_deferred
__io_queue_async_work
io_wq_enqueue
io_wqe_enqueue  // &wqe->lock

CPU1:
...
__io_uring_files_cancel
io_wq_cancel_cb
io_wqe_cancel_pending_work  // &wqe->lock
io_cancel_task_cb  // &ctx->completion_lock

Only __io_queue_deferred() calls queue_async_work() while holding
ctx->completion_lock, enqueue drained requests via io_req_task_queue()
instead.

Cc: stable@vger.kernel.org # 5.9+
Reported-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Tested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Begunkov 2021-01-26 23:35:10 +00:00 committed by Greg Kroah-Hartman
parent 256a0040c6
commit bc79ff0b1a
1 changed files with 2 additions and 8 deletions
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10
fs/io_uring.c
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@ -972,6 +972,7 @@ static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
const struct iovec *fast_iov,
struct iov_iter *iter, bool force);
static void io_req_drop_files(struct io_kiocb *req);
static void io_req_task_queue(struct io_kiocb *req);
static struct kmem_cache *req_cachep;
@ -1502,18 +1503,11 @@ static void __io_queue_deferred(struct io_ring_ctx *ctx)
do {
struct io_defer_entry *de = list_first_entry(&ctx->defer_list,
struct io_defer_entry, list);
struct io_kiocb *link;
if (req_need_defer(de->req, de->seq))
break;
list_del_init(&de->list);
/* punt-init is done before queueing for defer */
link = __io_queue_async_work(de->req);
if (link) {
__io_queue_linked_timeout(link);
/* drop submission reference */
io_put_req_deferred(link, 1);
}
io_req_task_queue(de->req);
kfree(de);
} while (!list_empty(&ctx->defer_list));
}