From: Tom Rix <trix@redhat.com>

Clang static analysis reports this warning

hooks.c:5765:6: warning: 4th function call argument is an uninitialized value
        if (selinux_xfrm_postroute_last(sksec->sid, skb, &ad, proto))
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

selinux_parse_skb() can return ok without setting proto.  The later call
to selinux_xfrm_postroute_last() does an early check of proto and can
return ok is the garbage proto value matches.  So initialize proto.

Fixes: eef9b41622f2 ("selinux: cleanup selinux_xfrm_sock_rcv_skb() and selinux_xfrm_postroute_last()")
Signed-off-by: Tom Rix <trix@redhat.com>
---
 security/selinux/hooks.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e2a6d0f5c47af..fd7a0e9e26647 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5742,7 +5742,7 @@ static unsigned int selinux_ip_postroute_compat(struct sk_buff *skb,
 	struct sk_security_struct *sksec;
 	struct common_audit_data ad;
 	struct lsm_network_audit net = {0,};
-	u8 proto;
+	u8 proto = 0;
 
 	sk = skb_to_full_sk(skb);
 	if (sk == NULL)
-- 
2.26.3

On Fri, Dec 24, 2021 at 10:07 AM <trix@redhat.com> wrote:
>
> From: Tom Rix <trix@redhat.com>
>
> Clang static analysis reports this warning
>
> hooks.c:5765:6: warning: 4th function call argument is an uninitialized value
>         if (selinux_xfrm_postroute_last(sksec->sid, skb, &ad, proto))
>             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> selinux_parse_skb() can return ok without setting proto.  The later call
> to selinux_xfrm_postroute_last() does an early check of proto and can
> return ok is the garbage proto value matches.  So initialize proto.
>
> Fixes: eef9b41622f2 ("selinux: cleanup selinux_xfrm_sock_rcv_skb() and selinux_xfrm_postroute_last()")
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>  security/selinux/hooks.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks Tom.  I don't think this is something that could be easily
triggered on a normal system, even if the compatibility mode was
enabled, but this is something that we should fix regardless.  I've
merged this into selinux/stable-5.16 and will send this up to Linus as
soon as it clears the normal automated testing.

-- 
paul moore
www.paul-moore.com