queue-4.19/tcp-fix-a-potential-null-pointer-dereference-in-tcp_.patch

   1 From 5c23cd9e25e811192c5daca46071464534414aad Mon Sep 17 00:00:00 2001
   2 From: Dust Li <dust.li@linux.alibaba.com>
   3 Date: Mon, 1 Apr 2019 16:04:53 +0800
   4 Subject: tcp: fix a potential NULL pointer dereference in tcp_sk_exit
   5
   6 [ Upstream commit b506bc975f60f06e13e74adb35e708a23dc4e87c ]
   7
   8  When tcp_sk_init() failed in inet_ctl_sock_create(),
   9  'net->ipv4.tcp_congestion_control' will be left
  10  uninitialized, but tcp_sk_exit() hasn't check for
  11  that.
  12
  13  This patch add checking on 'net->ipv4.tcp_congestion_control'
  14  in tcp_sk_exit() to prevent NULL-ptr dereference.
  15
  16 Fixes: 6670e1524477 ("tcp: Namespace-ify sysctl_tcp_default_congestion_control")
  17 Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
  18 Signed-off-by: Eric Dumazet <edumazet@google.com>
  19 Signed-off-by: David S. Miller <davem@davemloft.net>
  20 Signed-off-by: Sasha Levin <sashal@kernel.org>
  21 ---
  22  net/ipv4/tcp_ipv4.c | 3 ++-
  23  1 file changed, 2 insertions(+), 1 deletion(-)
  24
  25 diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
  26 index 30fdf891940b..11101cf8693b 100644
  27 --- a/net/ipv4/tcp_ipv4.c
  28 +++ b/net/ipv4/tcp_ipv4.c
  29 @@ -2490,7 +2490,8 @@ static void __net_exit tcp_sk_exit(struct net *net)
  30  {
  31         int cpu;
  32
  33 -       module_put(net->ipv4.tcp_congestion_control->owner);
  34 +       if (net->ipv4.tcp_congestion_control)
  35 +               module_put(net->ipv4.tcp_congestion_control->owner);
  36
  37         for_each_possible_cpu(cpu)
  38                 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.tcp_sk, cpu));
  39 --
  40 2.19.1
  41