The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Thanks, Sasha

------------------ original commit in Linus's tree ------------------

From 21f965221e7c42609521342403e8fb91b8b3e76e Mon Sep 17 00:00:00 2001

From: Jens Axboe axboe@kernel.dk Date: Sat, 14 Aug 2021 09:04:40 -0600 Subject: [PATCH] io_uring: only assign io_uring_enter() SQPOLL error in actual error case

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 --- 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 04c6d059ea94..6a092a534d2b 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -9370,9 +9370,10 @@ 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) {