From: Jens Axboe Date: Wed, 7 May 2025 14:07:09 +0000 (-0600) Subject: io_uring: ensure deferred completions are posted for multishot X-Git-Tag: v6.6.91~25 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=746e7d285dcb96caa1845fbbb62b14bf4010cdfb;p=thirdparty%2Fkernel%2Fstable.git io_uring: ensure deferred completions are posted for multishot 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 Reported-by: Christian Mazakas Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 4f4ac40fc6059..db592fa549b73 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -919,6 +919,14 @@ static bool __io_post_aux_cqe(struct io_ring_ctx *ctx, u64 user_data, s32 res, u { 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)