[PATCH 6.18 332/333] io_uring/eventfd: use ctx->rings_rcu for flags checking

Greg Kroah-Hartman
2026-03-17T17:28:50Z

From: Jens Axboe <axboe@kernel.dk>

Commit 177c69432161f6e4bab07ccacf8a1748a6898a6b upstream.

Similarly to what commit e78f7b70e837 did for local task work additions,
use ->rings_rcu under RCU rather than dereference ->rings directly. See
that commit for more details.

Cc: stable@vger.kernel.org
Fixes: 79cfe9e59c2a ("io_uring/register: add IORING_REGISTER_RESIZE_RINGS")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
io_uring/eventfd.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/io_uring/eventfd.c
+++ b/io_uring/eventfd.c
@@ -76,11 +76,15 @@ void io_eventfd_signal(struct io_ring_ct
{
bool skip = false;
struct io_ev_fd *ev_fd;
-
- if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
- return;
+ struct io_rings *rings;

guard(rcu)();
+
+ rings = rcu_dereference(ctx->rings_rcu);
+ if (!rings)
+ return;
+ if (READ_ONCE(rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
+ return;
ev_fd = rcu_dereference(ctx->io_ev_fd);
/*
* Check again if ev_fd exists in case an io_eventfd_unregister call