Commit f1d96a8f authored Mar 13, 2020 by Pavel Begunkov Committed by Jens Axboe Mar 14, 2020

io_uring: NULL-deref for IOSQE_{ASYNC,DRAIN}



Processing links, io_submit_sqe() prepares requests, drops sqes, and
passes them with sqe=NULL to io_queue_sqe(). There IOSQE_DRAIN and/or
IOSQE_ASYNC requests will go through the same prep, which doesn't expect
sqe=NULL and fail with NULL pointer deference.

Always do full prepare including io_alloc_async_ctx() for linked
requests, and then it can skip the second preparation.

Cc: stable@vger.kernel.org # 5.5
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 805b13ad

fs/io_uring.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -4131,6 +4131,9 @@ static int io_req_defer_prep(struct io_kiocb *req,
		{
		ssize_t ret = 0;

		if (!sqe)
		return 0;

		if (io_op_defs[req->opcode].file_table) {
		ret = io_grab_files(req);
		if (unlikely(ret))
		@@ -4907,6 +4910,11 @@ err_req:
		if (sqe_flags & (IOSQE_IO_LINK\|IOSQE_IO_HARDLINK)) {
		req->flags \|= REQ_F_LINK;
		INIT_LIST_HEAD(&req->link_list);

		if (io_alloc_async_ctx(req)) {
		ret = -EAGAIN;
		goto err_req;
		}
		ret = io_req_defer_prep(req, sqe);
		if (ret)
		req->flags \|= REQ_F_FAIL_LINK;

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