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@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
Tested-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index ef9db3e035062b189be8e408c15372e0dd11b3c6..2b313fe7003e4806d3e14e0dea0aa164fe1d8e11 100644 (file)
--- 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);