tcp: fix a potential NULL pointer dereference in tcp_sk_exit

Dust Li · davem330 · commit b506bc975f60 · 2019-04-01T10:11:41.000-07:00
When tcp_sk_init() failed in inet_ctl_sock_create(), 'net->ipv4.tcp_congestion_control' will be left uninitialized, but tcp_sk_exit() hasn't check for that. This patch add checking on 'net->ipv4.tcp_congestion_control' in tcp_sk_exit() to prevent NULL-ptr dereference. Fixes: 6670e15 ("tcp: Namespace-ify sysctl_tcp_default_congestion_control") Signed-off-by: Dust Li <dust.li@linux.alibaba.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
@@ -2578,7 +2578,8 @@ static void __net_exit tcp_sk_exit(struct net *net)
 {
 	int cpu;
 
-	module_put(net->ipv4.tcp_congestion_control->owner);
+	if (net->ipv4.tcp_congestion_control)
+		module_put(net->ipv4.tcp_congestion_control->owner);
 
 	for_each_possible_cpu(cpu)
 		inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.tcp_sk, cpu));

Original file line number	Diff line number	Diff line change
`@@ -2578,7 +2578,8 @@ static void __net_exit tcp_sk_exit(struct net *net)`
`2578`	`2578`	`{`
`2579`	`2579`	`int cpu;`
`2580`	`2580`
`2581`		`- module_put(net->ipv4.tcp_congestion_control->owner);`
	`2581`	`+ if (net->ipv4.tcp_congestion_control)`
	`2582`	`+ module_put(net->ipv4.tcp_congestion_control->owner);`
`2582`	`2583`
`2583`	`2584`	`for_each_possible_cpu(cpu)`
`2584`	`2585`	`inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.tcp_sk, cpu));`