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: 724a0845 ("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>

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);