linux-kernel - [PATCH] netlink: Safer deletion of sk_bind

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Date:	Mon, 1 Sep 2014 12:38:29 +0530
From:	Harish@...r.kernel.org, Jenny@...r.kernel.org, K@...r.kernel.org,
	N@...r.kernel.org
To:	<davem@...emloft.net>
CC:	<dborkman@...hat.com>, <tgraf@...g.ch>, <ebiederm@...ssion.com>,
	<darkjames-ws@...kjames.pl>, <rgb@...hat.com>,
	<eric.dumazet@...il.com>, <stephen@...workplumber.org>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH]     netlink: Safer deletion of sk_bind_node

From: Harish Jenny K N <harish_kandiga@...tor.com>

    Unable to handle kernel NULL pointer dereference at virtual address 00000000
        (netlink_release+0x0/0x2a0) from [<8034e78c>] (sock_release+0x28/0xa4)
        (sock_release+0x0/0xa4) from [<8034e830>] (sock_close+0x28/0x34)
        (sock_close+0x0/0x34) from [<800f3490>] (__fput+0xf0/0x1ec)
        (__fput+0x0/0x1ec) from [<800f3634>] (____fput+0x10/0x14)
        (____fput+0x0/0x14) from [<80040a64>] (task_work_run+0xb8/0xd8)
        (task_work_run+0x0/0xd8) from [<800113a0>] (do_work_pending+0xb0/0xc4)
        (do_work_pending+0x0/0xc4) from [<8000d960>] (work_pending+0xc/0x20)
    Call flow of the inline and static functions
        netlink_release
        -----netlink_remove
        ---------__sk_del_bind_node
        --------------__hlist_del

Signed-off-by: Harish Jenny K N <harish_kandiga@...tor.com>
---
 net/netlink/af_netlink.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index c416725..21a6b32 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1103,7 +1103,7 @@ static void netlink_remove(struct sock *sk)
 
 	netlink_table_grab();
 	if (nlk_sk(sk)->subscriptions)
-		__sk_del_bind_node(sk);
+		hlist_del_init(&sk->sk_bind_node);
 	netlink_table_ungrab();
 }
 
@@ -1382,7 +1382,7 @@ netlink_update_subscriptions(struct sock *sk, unsigned int subscriptions)
 	struct netlink_sock *nlk = nlk_sk(sk);
 
 	if (nlk->subscriptions && !subscriptions)
-		__sk_del_bind_node(sk);
+		hlist_del_init(&sk->sk_bind_node);
 	else if (!nlk->subscriptions && subscriptions)
 		sk_add_bind_node(sk, &nl_table[sk->sk_protocol].mc_list);
 	nlk->subscriptions = subscriptions;
-- 
1.7.9.5

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