6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jens Axboe axboe@kernel.dk
Commit 687b2bae0efff9b25e071737d6af5004e6e35af5 upstream.
Multishot normally uses io_req_post_cqe() to post completions, but when stopping it, it may finish up with a deferred completion. This is fine, except if another multishot event triggers before the deferred completions get flushed. If this occurs, then CQEs may get reordered in the CQ ring, and cause confusion on the application side.
When multishot posting via io_req_post_cqe(), flush any pending deferred completions first, if any.
Cc: stable@vger.kernel.org # 6.1+ Reported-by: Norman Maurer norman_maurer@apple.com Reported-by: Christian Mazakas christian.mazakas@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -919,6 +919,14 @@ static bool __io_post_aux_cqe(struct io_ { bool filled;
+ /* + * If multishot has already posted deferred completions, ensure that + * those are flushed first before posting this one. If not, CQEs + * could get reordered. + */ + if (!wq_list_empty(&ctx->submit_state.compl_reqs)) + __io_submit_flush_completions(ctx); + io_cq_lock(ctx); filled = io_fill_cqe_aux(ctx, user_data, res, cflags); if (!filled && allow_overflow)