2020-08-05 03:41:59

by Guoyu Huang

Subject: [PATCH] io_uring: Fix use-after-free in io_sq_wq_submit_work()

when ctx->sqo_mm is zero, io_sq_wq_submit_work() frees 'req'
without deleting it from 'task_list'. After that, 'req' is
accessed in io_ring_ctx_wait_and_kill() which lead to
a use-after-free.

Signed-off-by: Guoyu Huang <[email protected]>
---
fs/io_uring.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e0200406765c..4b5ac381c67f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2242,6 +2242,7 @@ static void io_sq_wq_submit_work(struct work_struct *work)
if (io_sqe_needs_user(sqe) && !cur_mm) {
if (!mmget_not_zero(ctx->sqo_mm)) {
ret = -EFAULT;
+ goto end_req;
} else {
cur_mm = ctx->sqo_mm;
use_mm(cur_mm);
--
2.25.1

2020-08-05 19:15:28

by Jens Axboe

Subject: Re: [PATCH] io_uring: Fix use-after-free in io_sq_wq_submit_work()

On 8/4/20 9:40 PM, Guoyu Huang wrote:
> when ctx->sqo_mm is zero, io_sq_wq_submit_work() frees 'req'
> without deleting it from 'task_list'. After that, 'req' is
> accessed in io_ring_ctx_wait_and_kill() which lead to
> a use-after-free.

This looks like an old one, that affects 5.4 only. I've massaged
it to apply on top of another fix, will ask to get it queued up for
stable. Thanks!

--
Jens Axboe