diff mbox

[net] selinux: fix random read in selinux_ip_postroute_compat()

Message ID 1446759564.4184.65.camel@edumazet-glaptop2.roam.corp.google.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Eric Dumazet Nov. 5, 2015, 9:39 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

In commit e446f9dfe17b ("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: ca6fb0651883 ("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>
---
 security/selinux/hooks.c |   18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)



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Comments

David Miller Nov. 5, 2015, 9:46 p.m. UTC | #1 
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 05 Nov 2015 13:39:24 -0800

> From: Eric Dumazet <edumazet@google.com>
> 
> In commit e446f9dfe17b ("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: ca6fb0651883 ("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>

Looks good, applied, thanks Eric!
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Dmitry Vyukov Nov. 6, 2015, 1:52 p.m. UTC | #2 
On Thu, Nov 5, 2015 at 10:46 PM, David Miller <davem@davemloft.net> wrote:
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Thu, 05 Nov 2015 13:39:24 -0800
>
>> From: Eric Dumazet <edumazet@google.com>
>>
>> In commit e446f9dfe17b ("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: ca6fb0651883 ("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>
>
> Looks good, applied, thanks Eric!

Fixed the issue for me.
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Eric Dumazet Nov. 6, 2015, 2:46 p.m. UTC | #3 
On Fri, 2015-11-06 at 14:52 +0100, Dmitry Vyukov wrote:

> Fixed the issue for me.

Thanks Dmitry

I'll submit ~6 additional patches, after doing a long due audit.


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diff mbox

Patch

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 26f4039d54b8..c9b2d5467477 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -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;