net: core: null pointer derefernce in sockev_client_cb

sockev_client_cb creates a netlink message and populates
the nlmsg_data using the socket->sock information.
If socket is closed, while the nlmsg_data is being
populated, a null pointer dereference occurs.

BUG: KASAN: null-ptr-deref in sockev_client_cb+0x1e4/0x310 net/core/sockev_nlmcast.c:98
Read of size 2 at addr 0000000000000010 by task syz-executor/9398
CPU: 6 PID: 9398 Comm: syz-executor Tainted: G W O 4.9.92+ #1

Call trace:
[<ffffff94e2bebec4>] sockev_client_cb+0x1e4/0x310 net/core/sockev_nlmcast.c:98
[<ffffff94e14fb20c>] notifier_call_chain+0x94/0xe0 kernel/notifier.c:93
[<ffffff94e14fb894>] __blocking_notifier_call_chain+0x6c/0xb8 kernel/notifier.c:317
[<ffffff94e14fb920>] blocking_notifier_call_chain+0x40/0x50 kernel/notifier.c:328
[<ffffff94e2b727f8>] sockev_notify net/socket.c:180 [inline]
[<ffffff94e2b727f8>] SYSC_listen net/socket.c:1446 [inline]
[<ffffff94e2b727f8>] SyS_listen+0x1e0/0x1f8 net/socket.c:1428
[<ffffff94e1483f70>] el0_svc_naked+0x24/0x28

CR's Fixed: 2251042
Change-Id: Iad9eb58cd05fcdc0b5cc1ed24de56b69abb532b4
Signed-off-by: Sharath Chandra Vurukala <sharathv@codeaurora.org>
Signed-off-by: Tejaswi Tanikella <tejaswit@codeaurora.org>

diff --git a/net/core/sockev_nlmcast.c b/net/core/sockev_nlmcast.c
index 88bb411..bade2d2 100644 (file)
--- a/net/core/sockev_nlmcast.c
+++ b/net/core/sockev_nlmcast.c
@@ -70,14 +70,17 @@ static int sockev_client_cb(struct notifier_block *nb,
        struct nlmsghdr *nlh;
        struct sknlsockevmsg *smsg;
        struct socket *sock;
+       struct sock *sk;
 
        sock = (struct socket *)data;
-       if (socknlmsgsk == 0)
+       if (!socknlmsgsk || !sock)
                goto done;
-       if ((!socknlmsgsk) || (!sock) || (!sock->sk))
+
+       sk = sock->sk;
+       if (!sk)
                goto done;
 
-       if (sock->sk->sk_family != AF_INET && sock->sk->sk_family != AF_INET6)
+       if (sk->sk_family != AF_INET && sk->sk_family != AF_INET6)
                goto done;
 
        if (event != SOCKEV_BIND && event != SOCKEV_LISTEN)
@@ -98,12 +101,11 @@ static int sockev_client_cb(struct notifier_block *nb,
        smsg = nlmsg_data(nlh);
        smsg->pid = current->pid;
        _sockev_event(event, smsg->event, sizeof(smsg->event));
-       smsg->skfamily = sock->sk->sk_family;
-       smsg->skstate = sock->sk->sk_state;
-       smsg->skprotocol = sock->sk->sk_protocol;
-       smsg->sktype = sock->sk->sk_type;
-       smsg->skflags = sock->sk->sk_flags;
-
+       smsg->skfamily = sk->sk_family;
+       smsg->skstate = sk->sk_state;
+       smsg->skprotocol = sk->sk_protocol;
+       smsg->sktype = sk->sk_type;
+       smsg->skflags = sk->sk_flags;
        nlmsg_notify(socknlmsgsk, skb, 0, SKNLGRP_SOCKEV, 0, GFP_KERNEL);
 done:
        return 0;