commit dfea9fce29fda6f2f91161677e0e0d9b671bc099 upstream.

The purpose of io_uring_cancel_files() is to wait for all requests matching ->files to go/be cancelled. We should first drop files of a request in io_req_drop_files() and only then make it undiscoverable for io_uring_cancel_files.

First drop, then delete from list. It's ok to leave req->id->files dangling, because it's not dereferenced by cancellation code, only compared against. It would potentially go to sleep and be awaken by following in io_req_drop_files() wake_up().

Fixes: 0f2122045b946 ("io_uring: don't rely on weak ->files references") Cc: stable@vger.kernel.org # 5.5+ Signed-off-by: Pavel Begunkov asml.silence@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk --- fs/io_uring.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c index 86dac2b2e276..dfe33b0b148f 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5854,15 +5854,15 @@ static void io_req_drop_files(struct io_kiocb *req) struct io_ring_ctx *ctx = req->ctx; unsigned long flags;

+ put_files_struct(req->work.identity->files); + put_nsproxy(req->work.identity->nsproxy); spin_lock_irqsave(&ctx->inflight_lock, flags); list_del(&req->inflight_entry); - if (waitqueue_active(&ctx->inflight_wait)) - wake_up(&ctx->inflight_wait); spin_unlock_irqrestore(&ctx->inflight_lock, flags); req->flags &= ~REQ_F_INFLIGHT; - put_files_struct(req->work.identity->files); - put_nsproxy(req->work.identity->nsproxy); req->work.flags &= ~IO_WQ_WORK_FILES; + if (waitqueue_active(&ctx->inflight_wait)) + wake_up(&ctx->inflight_wait); }

static void __io_clean_op(struct io_kiocb *req)