io_uring: only assign io_uring_enter() SQPOLL error in actual error case

stable inclusion
from stable-5.10.61
commit f15e6426739389876d66d093f49866b4f24c1a4b
bugzilla: 177029 https://gitee.com/openeuler/kernel/issues/I4EAXD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f15e6426739389876d66d093f49866b4f24c1a4b

--------------------------------

[ upstream commit 21f96522 ]

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: d9d05217 ("io_uring: stop SQPOLL submit on creator's death")
Reported-by: Sherlock Holo sherlockya@gmail.com
Link: https://github.com/axboe/liburing/issues/413Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/io_uring.c

@@ -9078,9 +9078,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 	if (ctx->flags & IORING_SETUP_SQPOLL) {
 		io_cqring_overflow_flush(ctx, false, NULL, NULL);
 
-		ret = -EOWNERDEAD;
-		if (unlikely(ctx->sqo_dead))
+		if (unlikely(ctx->sqo_dead)) {
+			ret = -EOWNERDEAD;
 			goto out;
+		}
 		if (flags & IORING_ENTER_SQ_WAKEUP)
 			wake_up(&ctx->sq_data->wait);
 		if (flags & IORING_ENTER_SQ_WAIT) {