[PATCH 5.12] io_uring: fix EIOCBQUEUED iter revert

[PATCH 5.12] io_uring: fix EIOCBQUEUED iter revert

[Pavel Begunkov]

iov_iter_revert() is done in completion handlers that happensf before
read/write returns -EIOCBQUEUED, no need to repeat reverting afterwards.
Moreover, even though it may appear being just a no-op, it's actually
races with 1) user forging a new iovec of a different size 2) reissue,
that is done via io-wq continues completely asynchronously.

Fixes: 3e6a0d3c7571c ("io_uring: fix -EAGAIN retry with IOPOLL")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---

p.s. same is already done for-5.13 as a part of a larger patch,
should be trivial to merge.

 fs/io_uring.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c8ceb5ef66a7..3cd8bfe554e2 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3284,8 +3284,6 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
 	ret = io_iter_do_read(req, iter);
 
 	if (ret == -EIOCBQUEUED) {
-		if (req->async_data)
-			iov_iter_revert(iter, io_size - iov_iter_count(iter));
 		goto out_free;
 	} else if (ret == -EAGAIN) {
 		/* IOPOLL retry should happen for io-wq threads */
@@ -3418,8 +3416,6 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
 	/* no retry on NONBLOCK nor RWF_NOWAIT */
 	if (ret2 == -EAGAIN && (req->flags & REQ_F_NOWAIT))
 		goto done;
-	if (ret2 == -EIOCBQUEUED && req->async_data)
-		iov_iter_revert(iter, io_size - iov_iter_count(iter));
 	if (!force_nonblock || ret2 != -EAGAIN) {
 		/* IOPOLL retry should happen for io-wq threads */
 		if ((req->ctx->flags & IORING_SETUP_IOPOLL) && ret2 == -EAGAIN)
-- 
2.24.0