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selinux: fix random read in selinux_ip_postroute_compat()

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In commit e446f9dfe1 ("net: synack packets can be attached to request
sockets"), I missed one remaining case of invalid skb->sk->sk_security
access.

Dmitry Vyukov got a KASan report pointing to it.

Add selinux_skb_sk() helper that is responsible to get back to the
listener if skb is attached to a request socket, instead of
duplicating the logic.

Fixes: ca6fb06518 ("tcp: attach SYNACK messages to request sockets instead of listener")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-11-05 13:39:24 -08:00 committed by David S. Miller
parent 432599d7a7
commit 212cd08953
1 changed files with 14 additions and 4 deletions
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18
security/selinux/hooks.c
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@ -4931,11 +4931,23 @@ static unsigned int selinux_ipv4_output(void *priv,
return selinux_ip_output(skb, PF_INET);
}
/* SYNACK messages might be attached to request sockets.
* To get back to sk_security, we need to look at the listener.
*/
static struct sock *selinux_skb_sk(const struct sk_buff *skb)
{
struct sock *sk = skb->sk;
if (sk && sk->sk_state == TCP_NEW_SYN_RECV)
sk = inet_reqsk(sk)->rsk_listener;
return sk;
}
static unsigned int selinux_ip_postroute_compat(struct sk_buff *skb,
int ifindex,
u16 family)
{
struct sock *sk = skb->sk;
struct sock *sk = selinux_skb_sk(skb);
struct sk_security_struct *sksec;
struct common_audit_data ad;
struct lsm_network_audit net = {0,};
@ -4990,7 +5002,7 @@ static unsigned int selinux_ip_postroute(struct sk_buff *skb,
if (!secmark_active && !peerlbl_active)
return NF_ACCEPT;
sk = skb->sk;
sk = selinux_skb_sk(skb);
#ifdef CONFIG_XFRM
/* If skb->dst->xfrm is non-NULL then the packet is undergoing an IPsec
@ -5035,8 +5047,6 @@ static unsigned int selinux_ip_postroute(struct sk_buff *skb,
u32 skb_sid;
struct sk_security_struct *sksec;
if (sk->sk_state == TCP_NEW_SYN_RECV)
sk = inet_reqsk(sk)->rsk_listener;
sksec = sk->sk_security;
if (selinux_skb_peerlbl_sid(skb, family, &skb_sid))
return NF_DROP;