[PATCH 5.10 511/717] io_uring: fix racy IOPOLL completions

Greg Kroah-Hartman
2020-12-28T14:44:50Z

From: Pavel Begunkov <asml.silence@gmail.com>

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>

---
fs/io_uring.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3944,11 +3944,17 @@ static int io_remove_buffers(struct io_k
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_
}
}
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;
}