[PATCH 5.13 103/127] io_uring: only assign io_uring_enter() SQPOLL error in actual error case

Sasha Levin
2021-08-24T17:03:06Z

From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 21f965221e7c42609521342403e8fb91b8b3e76e ]

If an SQPOLL based ring is newly created and an application issues an
io_uring_enter(2) system call on it, then we can return a spurious
-EOWNERDEAD error. This happens because there's nothing to submit, and
if the caller doesn't specify any other action, the initial error
assignment of -EOWNERDEAD never gets overwritten. This causes us to
return it directly, even if it isn't valid.

Move the error assignment into the actual failure case instead.

Cc: stable@vger.kernel.org
Fixes: d9d05217cb69 ("io_uring: stop SQPOLL submit on creator's death")
Reported-by: Sherlock Holo sherlockya@gmail.com
Link: https://github.com/axboe/liburing/issues/413
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 00746109e0c8..221b80ae831f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9362,9 +9362,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
if (ctx->flags & IORING_SETUP_SQPOLL) {
io_cqring_overflow_flush(ctx, false);

- ret = -EOWNERDEAD;
- if (unlikely(ctx->sq_data->thread == NULL))
+ if (unlikely(ctx->sq_data->thread == NULL)) {
+ ret = -EOWNERDEAD;
goto out;
+ }
if (flags & IORING_ENTER_SQ_WAKEUP)
wake_up(&ctx->sq_data->wait);
if (flags & IORING_ENTER_SQ_WAIT) {
--
2.30.2