[PATCH 5.0 024/117] tcp: fix a potential NULL pointer dereference in tcp_sk_exit

Greg Kroah-Hartman
2019-04-15T19:19:55Z

[ Upstream commit b506bc975f60f06e13e74adb35e708a23dc4e87c ]

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: 6670e1524477 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/tcp_ipv4.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1aae9ab57fe9..00852f47a73d 100644
--- 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));
--
2.19.1