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Date:   Tue, 4 Aug 2020 20:40:42 -0700
From:   Guoyu Huang <hgy5945@gmail.com>
To:     axboe@kernel.dk, viro@zeniv.linux.org.uk
Cc:     linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] io_uring: Fix use-after-free in io_sq_wq_submit_work()
Message-ID: <20200805034042.GA29805@ubuntu>
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Sender: linux-kernel-owner@vger.kernel.org
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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 <hgy5945@gmail.com>
---
 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