From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sun, 6 Dec 2020 22:22:43 +0000 (+0000)
Subject: io_uring: fix racy IOPOLL completions
X-Git-Tag: v5.10.7~437
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f961c2b496e60214a5913857958238e6ca0e1c0e;p=platform%2Fkernel%2Flinux-rpi.git

io_uring: fix racy IOPOLL completions

commit 31bff9a51b264df6d144931a6a5f1d6cc815ed4b upstream.

IOPOLL allows buffer remove/provide requests, but they doesn't
synchronise by rules of IOPOLL, namely it have to hold uring_lock.

Cc: <stable@vger.kernel.org> # 5.7+
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>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 443b021..a1f0c8a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3944,11 +3944,17 @@ static int io_remove_buffers(struct io_kiocb *req, bool force_nonblock,
 	head = idr_find(&ctx->io_buffer_idr, p->bgid);
 	if (head)
 		ret = __io_remove_buffers(ctx, head, p->bgid, p->nbufs);
-
-	io_ring_submit_lock(ctx, !force_nonblock);
 	if (ret < 0)
 		req_set_fail_links(req);
-	__io_req_complete(req, ret, 0, cs);
+
+	/* need to hold the lock to complete IOPOLL requests */
+	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		__io_req_complete(req, ret, 0, cs);
+		io_ring_submit_unlock(ctx, !force_nonblock);
+	} else {
+		io_ring_submit_unlock(ctx, !force_nonblock);
+		__io_req_complete(req, ret, 0, cs);
+	}
 	return 0;
 }
 
@@ -4033,10 +4039,17 @@ static int io_provide_buffers(struct io_kiocb *req, bool force_nonblock,
 		}
 	}
 out:
-	io_ring_submit_unlock(ctx, !force_nonblock);
 	if (ret < 0)
 		req_set_fail_links(req);
-	__io_req_complete(req, ret, 0, cs);
+
+	/* need to hold the lock to complete IOPOLL requests */
+	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		__io_req_complete(req, ret, 0, cs);
+		io_ring_submit_unlock(ctx, !force_nonblock);
+	} else {
+		io_ring_submit_unlock(ctx, !force_nonblock);
+		__io_req_complete(req, ret, 0, cs);
+	}
 	return 0;
 }