We can't just go over linked requests because it may race with linked timeouts. Take ctx->completion_lock in that case.

Cc: stable@vger.kernel.org # v5.7+ Signed-off-by: Pavel Begunkov asml.silence@gmail.com --- fs/io_uring.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c index 29f1417690d5..8018c7076b25 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -8470,7 +8470,21 @@ static bool io_timeout_remove_link(struct io_ring_ctx *ctx,

static bool io_cancel_link_cb(struct io_wq_work *work, void *data) { - return io_match_link(container_of(work, struct io_kiocb, work), data); + struct io_kiocb *req = container_of(work, struct io_kiocb, work); + bool ret; + + if (req->flags & REQ_F_LINK_TIMEOUT) { + unsigned long flags; + struct io_ring_ctx *ctx = req->ctx; + + /* protect against races with linked timeouts */ + spin_lock_irqsave(&ctx->completion_lock, flags); + ret = io_match_link(req, data); + spin_unlock_irqrestore(&ctx->completion_lock, flags); + } else { + ret = io_match_link(req, data); + } + return ret; }

static void io_attempt_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req)