io_uring: prevent speculating sq_array indexing

The SQ index array consists of user provided indexes, which io_uring
then uses to index the SQ, and so it's susceptible to speculation. For
all other queues io_uring tracks heads and tails in kernel, and they
shouldn't need any special care.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c6c7a25962924a55869e317e4fdb682dfdc6b279.1730687889.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 7c1ca36b117b38ed00ceb9943761c708cd48ddc5..751b9e19da6eb53671789b2a22c6159870edb51b 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2245,6 +2245,7 @@ static bool io_get_sqe(struct io_ring_ctx *ctx, const struct io_uring_sqe **sqe)
                                   READ_ONCE(ctx->rings->sq_dropped) + 1);
                        return false;
                }
+               head = array_index_nospec(head, ctx->sq_entries);
        }
 
        /*