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io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period

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Commit c9a40292a4 upstream.

io_eventfd_do_signal() is invoked from an RCU callback, but when
dropping the reference to the io_ev_fd, it calls io_eventfd_free()
directly if the refcount drops to zero. This isn't correct, as any
potential freeing of the io_ev_fd should be deferred another RCU grace
period.

Just call io_eventfd_put() rather than open-code the dec-and-test and
free, which will correctly defer it another RCU grace period.

Fixes: 21a091b970 ("io_uring: signal registered eventfd to process deferred task work")
Reported-by: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jens Axboe 2025-01-08 10:28:05 -07:00 committed by Greg Kroah-Hartman
parent cbb64f5d75
commit a7085c3ae4
1 changed files with 1 additions and 1 deletions
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2
io_uring/eventfd.c
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@ -38,7 +38,7 @@ static void io_eventfd_do_signal(struct rcu_head *rcu)
eventfd_signal_mask(ev_fd->cq_ev_fd, EPOLL_URING_WAKE);
if (refcount_dec_and_test(&ev_fd->refs))
io_eventfd_free(rcu);
call_rcu(&ev_fd->rcu, io_eventfd_free);
}
void io_eventfd_signal(struct io_ring_ctx *ctx)