From abdad709ed8fe4fd3b865ed1010de37a49601ff4 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Sat, 19 Mar 2022 18:04:41 -0600 Subject: [PATCH] io_uring: recycle provided before arming poll We currently have a race where we recycle the selected buffer if poll returns IO_APOLL_OK. But that's too late, as the poll could already be triggering or have triggered. If that race happens, then we're putting a buffer that's already being used. Fix this by recycling before we arm poll. This does mean that we'll sometimes almost instantly re-select the buffer, but it's rare enough in testing that it should not pose a performance issue. Fixes: b1c62645758e ("io_uring: recycle provided buffers if request goes async") Signed-off-by: Jens Axboe --- fs/io_uring.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 5fa7363..9894934 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -6240,6 +6240,8 @@ static int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags) req->flags |= REQ_F_POLLED; ipt.pt._qproc = io_async_queue_proc; + io_kbuf_recycle(req); + ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask); if (ret || ipt.error) return ret ? IO_APOLL_READY : IO_APOLL_ABORTED; @@ -7491,7 +7493,6 @@ static void io_queue_sqe_arm_apoll(struct io_kiocb *req) io_queue_async_work(req, NULL); break; case IO_APOLL_OK: - io_kbuf_recycle(req); break; } -- 2.7.4