linux-kernel - [PATCH][next] netfilter: conntrack: fix an unsigned int comparison to less than zero

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Message-Id: <20200526180706.199338-1-colin.king@canonical.com>
Date:   Tue, 26 May 2020 19:07:06 +0100
From:   Colin King <colin.king@...onical.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] netfilter: conntrack: fix an unsigned int comparison to less than zero

From: Colin Ian King <colin.king@...onical.com>

The error check to see if protoff is less than zero is always false
because it is a unsigned int.  The call to ipv6_skip_exthdr can return
negative values for an error so cast protoff to int to fix this check.

Addresses-Coverity: ("Macro compares unsigned to 0 (no effect)")
Fixes: ee04805ff54a ("netfilter: conntrack: make conntrack userspace helpers work again")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 net/netfilter/nf_conntrack_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 08e0c19f6b39..2933b96a90c6 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2114,7 +2114,7 @@ static int nf_confirm_cthelper(struct sk_buff *skb, struct nf_conn *ct,
 		pnum = ipv6_hdr(skb)->nexthdr;
 		protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &pnum,
 					   &frag_off);
-		if (protoff < 0 || (frag_off & htons(~0x7)) != 0)
+		if ((int)protoff < 0 || (frag_off & htons(~0x7)) != 0)
 			return 0;
 		break;
 	}
-- 
2.25.1