[PATCH v2] io_uring: check for user passing 0 nr_submit

[Pavel Begunkov <asml.silence@gmail.com>]

io_submit_sqes() shouldn't be stepping into its main loop when there is
nothing to submit, i.e. nr=0. Fix 0 submission queue entries checks,
which should follow after all user input truncations.

Cc: stable@vger.kernel.org
Fixes: 6962980947e2b ("io_uring: restructure submit sqes to_submit checks")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---

v2: split out of the series with extra tags, no functional changes

 io_uring/io_uring.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 820ef0527666..ee04ab9bf968 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2422,10 +2422,11 @@ int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
 	unsigned int left;
 	int ret;
 
+	entries = min(nr, entries);
 	if (unlikely(!entries))
 		return 0;
-	/* make sure SQ entry isn't read before tail */
-	ret = left = min(nr, entries);
+
+	ret = left = entries;
 	io_get_task_refs(left);
 	io_submit_state_start(&ctx->submit_state, left);
 
-- 
2.49.0