36b5095b07
[ Upstream commit 69e16d01d1de4f1249869de342915f608feb55d5 ]
l2tp_tunnel_register() registers a tunnel without fully
initializing its attribute. This can allow another kernel thread
running l2tp_xmit_core() to access the uninitialized data and
then cause a kernel NULL pointer dereference error, as shown below.
Thread 1 Thread 2
//l2tp_tunnel_register()
list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
//pppol2tp_connect()
tunnel = l2tp_tunnel_get(sock_net(sk), info.tunnel_id);
// Fetch the new tunnel
...
//l2tp_xmit_core()
struct sock *sk = tunnel->sock;
...
bh_lock_sock(sk);
//Null pointer error happens
tunnel->sock = sk;
Fix this bug by initializing tunnel->sock before adding the
tunnel into l2tp_tunnel_list.
Reviewed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Sishuai Gong <sishuai@purdue.edu>
Reported-by: Sishuai Gong <sishuai@purdue.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: b68777d54fac ("l2tp: Serialize access to sk_user_data with sk_callback_lock")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.