From f1d96a8fcbbbb22d4fbc1d69eaaa678bbb0ff6e2 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Fri, 13 Mar 2020 22:29:14 +0300
Subject: [PATCH] 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>
---
fs/io_uring.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1b2517291b787..b1fbc4424aa63 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -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 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
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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