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Since the ppp socket/session lifetime rework, session teardown runs asynchronously and can clear sk_user_data and drop the last session reference in parallel with ioctl(). This leaves ioctl() with a stale session pointer and can trigger a use-after-free. Fix this by using pppol2tp_sock_to_session() in pppol2tp_ioctl() and dropping the session reference before returning. This matches the existing getsockopt/setsockopt paths. Fixes: c5cbaef992d64 ("l2tp: refactor ppp socket/session relationship") Signed-off-by: Yiqi Sun --- net/l2tp/l2tp_ppp.c | 88 +++++++++++++++++++++++++++------------------ 1 file changed, 54 insertions(+), 34 deletions(-) diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c index ae4543d5597b..e6d7d3537180 100644 --- a/net/l2tp/l2tp_ppp.c +++ b/net/l2tp/l2tp_ppp.c @@ -1042,66 +1042,79 @@ static int pppol2tp_tunnel_copy_stats(struct pppol2tp_ioc_stats *stats, static int pppol2tp_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) { + struct sock *sk = sock->sk; struct pppol2tp_ioc_stats stats; struct l2tp_session *session; + int err; + + err = -ENOTCONN; + if (!sk->sk_user_data) + goto end; + + err = -EBADF; + session = pppol2tp_sock_to_session(sk); + if (!session) + goto end; switch (cmd) { case PPPIOCGMRU: case PPPIOCGFLAGS: - session = sock->sk->sk_user_data; - if (!session) - return -ENOTCONN; - if (WARN_ON(session->magic != L2TP_SESSION_MAGIC)) - return -EBADF; + goto end_put_sess; /* Not defined for tunnels */ - if (!session->session_id && !session->peer_session_id) - return -ENOSYS; + if (!session->session_id && !session->peer_session_id) { + err = -ENOSYS; + goto end_put_sess; + } - if (put_user(0, (int __user *)arg)) - return -EFAULT; + if (put_user(0, (int __user *)arg)) { + err = -EFAULT; + goto end_put_sess; + } + err = 0; break; case PPPIOCSMRU: case PPPIOCSFLAGS: - session = sock->sk->sk_user_data; - if (!session) - return -ENOTCONN; - if (WARN_ON(session->magic != L2TP_SESSION_MAGIC)) - return -EBADF; + goto end_put_sess; /* Not defined for tunnels */ - if (!session->session_id && !session->peer_session_id) - return -ENOSYS; + if (!session->session_id && !session->peer_session_id) { + err = -ENOSYS; + goto end_put_sess; + } - if (!access_ok((int __user *)arg, sizeof(int))) - return -EFAULT; + if (!access_ok((int __user *)arg, sizeof(int))) { + err = -EFAULT; + goto end_put_sess; + } + err = 0; break; case PPPIOCGL2TPSTATS: - session = sock->sk->sk_user_data; - if (!session) - return -ENOTCONN; - if (WARN_ON(session->magic != L2TP_SESSION_MAGIC)) - return -EBADF; + goto end_put_sess; /* Session 0 represents the parent tunnel */ if (!session->session_id && !session->peer_session_id) { u32 session_id; - int err; + int rc; if (copy_from_user(&stats, (void __user *)arg, - sizeof(stats))) - return -EFAULT; + sizeof(stats))) { + err = -EFAULT; + goto end_put_sess; + } session_id = stats.session_id; - err = pppol2tp_tunnel_copy_stats(&stats, - session->tunnel); - if (err < 0) - return err; + rc = pppol2tp_tunnel_copy_stats(&stats, + session->tunnel); + if (rc < 0) { + err = rc; + goto end_put_sess; + } stats.session_id = session_id; } else { @@ -1111,15 +1124,22 @@ static int pppol2tp_ioctl(struct socket *sock, unsigned int cmd, stats.tunnel_id = session->tunnel->tunnel_id; stats.using_ipsec = l2tp_tunnel_uses_xfrm(session->tunnel); - if (copy_to_user((void __user *)arg, &stats, sizeof(stats))) - return -EFAULT; + if (copy_to_user((void __user *)arg, &stats, sizeof(stats))) { + err = -EFAULT; + goto end_put_sess; + } + err = 0; break; default: - return -ENOIOCTLCMD; + err = -ENOIOCTLCMD; + break; } - return 0; +end_put_sess: + l2tp_session_put(session); +end: + return err; } /***************************************************************************** -- 2.34.1