linux-kernel - [PATCH] fuse: Avoid potential use after free

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Message-Id: <20210406235332.2206460-1-pakki001@umn.edu>
Date:   Tue,  6 Apr 2021 18:53:32 -0500
From:   Aditya Pakki <pakki001@....edu>
To:     pakki001@....edu
Cc:     Vivek Goyal <vgoyal@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        virtualization@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] fuse: Avoid potential use after free

In virtio_fs_get_tree, after fm is freed, it is again freed in case
s_root is NULL and virtio_fs_fill_super() returns an error. To avoid
a double free, set fm to NULL.

Signed-off-by: Aditya Pakki <pakki001@....edu>
---
 fs/fuse/virtio_fs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 4ee6f734ba83..a7484c1539bf 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -1447,6 +1447,7 @@ static int virtio_fs_get_tree(struct fs_context *fsc)
 	if (fsc->s_fs_info) {
 		fuse_conn_put(fc);
 		kfree(fm);
+		fm = NULL;
 	}
 	if (IS_ERR(sb))
 		return PTR_ERR(sb);
-- 
2.25.1