On 3/23/20 8:36 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 5.5-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Here's a tested backport, thanks for letting us know!
>From f1d96a8fcbbbb22d4fbc1d69eaaa678bbb0ff6e2 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
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@xxxxxxxxxxxxxxx # 5.5
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2547c6395d5e..5383b225e48e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3097,6 +3097,9 @@ static int io_req_defer_prep(struct io_kiocb *req,
{
ssize_t ret = 0;
+ if (!sqe)
+ return 0;
+
switch (req->opcode) {
case IORING_OP_NOP:
break;
@@ -3680,6 +3683,11 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
req->flags |= REQ_F_HARDLINK;
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;
--
Jens Axboe
