diff mbox

[net] ipv6: tcp: fix race in IPV6_2292PKTOPTIONS

Message ID 1421840742.4832.24.camel@edumazet-glaptop2.roam.corp.google.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Eric Dumazet Jan. 21, 2015, 11:45 a.m. UTC 
From: Eric Dumazet <edumazet@google.com>

IPv6 TCP sockets store in np->pktoptions skbs, and use skb_set_owner_r()
to charge the skb to socket.

It means that destructor must be called while socket is locked.

Therefore, we cannot use skb_get() or atomic_inc(&skb->users)
to protect ourselves : kfree_skb() might race with other users
manipulating sk->sk_forward_alloc

Fix this race by holding socket lock for the duration of
ip6_datagram_recv_ctl()

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 Since this bug is very old, feel free to apply on net-next ;)

 net/ipv6/ipv6_sockglue.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)



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Comments

David Miller Jan. 26, 2015, 8:44 a.m. UTC | #1 
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 21 Jan 2015 03:45:42 -0800

> From: Eric Dumazet <edumazet@google.com>
> 
> IPv6 TCP sockets store in np->pktoptions skbs, and use skb_set_owner_r()
> to charge the skb to socket.
> 
> It means that destructor must be called while socket is locked.
> 
> Therefore, we cannot use skb_get() or atomic_inc(&skb->users)
> to protect ourselves : kfree_skb() might race with other users
> manipulating sk->sk_forward_alloc
> 
> Fix this race by holding socket lock for the duration of
> ip6_datagram_recv_ctl()
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  Since this bug is very old, feel free to apply on net-next ;)

Applied to net-next, thanks Eric.
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diff mbox

Patch

diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 66980d8d98d1f5b3ef7a50dc33cb9b617f25604d..8d766d9100cba408525faf5818b7b0c6b6bc543c 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -996,13 +996,9 @@  static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		lock_sock(sk);
 		skb = np->pktoptions;
 		if (skb)
-			atomic_inc(&skb->users);
-		release_sock(sk);
-
-		if (skb) {
 			ip6_datagram_recv_ctl(sk, &msg, skb);
-			kfree_skb(skb);
-		} else {
+		release_sock(sk);
+		if (!skb) {
 			if (np->rxopt.bits.rxinfo) {
 				struct in6_pktinfo src_info;
 				src_info.ipi6_ifindex = np->mcast_oif ? np->mcast_oif :