linux-kernel - [PATCH next] fs/9p: fix uaf in in v9fs_stat2inode

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Date: Fri, 2 Feb 2024 20:15:31 +0800
From: Lizhi Xu <lizhi.xu@...driver.com>
To: <syzbot+7a3d75905ea1a830dbe5@...kaller.appspotmail.com>
CC: <asmadeus@...ewreck.org>, <ericvh@...nel.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux_oss@...debyte.com>, <lucho@...kov.net>,
        <syzkaller-bugs@...glegroups.com>, <v9fs@...ts.linux.dev>
Subject: [PATCH next] fs/9p: fix uaf in in v9fs_stat2inode_dotl

The incorrect logical order of accessing the st object code in v9fs_fid_iget_dotl
is causing this uaf.

Fixes: 724a08450f74 ("fs/9p: simplify iget to remove unnecessary paths")
Reported-and-tested-by: syzbot+7a3d75905ea1a830dbe5@...kaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
---
 fs/9p/vfs_inode_dotl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index ef9db3e03506..2b313fe7003e 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -78,11 +78,11 @@ struct inode *v9fs_fid_iget_dotl(struct super_block *sb, struct p9_fid *fid)
 
 	retval = v9fs_init_inode(v9ses, inode, &fid->qid,
 				 st->st_mode, new_decode_dev(st->st_rdev));
+	v9fs_stat2inode_dotl(st, inode, 0);
 	kfree(st);
 	if (retval)
 		goto error;
 
-	v9fs_stat2inode_dotl(st, inode, 0);
 	v9fs_set_netfs_context(inode);
 	v9fs_cache_inode_get_cookie(inode);
 	retval = v9fs_get_acl(inode, fid);
-- 
2.43.0