io_uring/zcrx: recheck ifq on shutdown

io_ring_exit_work() checks ifq before shutting it down and guarantees
that the pointer is stable, but instead of relying on rather complicated
synchronisation recheck the ifq pointer inside.

Reported-by: Kees Bakker <kees@ijzerbout.nl>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/905e55c47235ab26377a735294f939f31d00ae53.1739934175.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 026efb8dd381448db11eb95f29efec0a5c8ea0a7..a9eaab3fccf21ae9cce7a8513b9d57082d062327 100644 (file)
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -489,9 +489,9 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
 {
        lockdep_assert_held(&ctx->uring_lock);
 
-       if (ctx->ifq)
-               io_zcrx_scrub(ctx->ifq);
-
+       if (!ctx->ifq)
+               return;
+       io_zcrx_scrub(ctx->ifq);
        io_close_queue(ctx->ifq);
 }