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Date:   Mon, 22 Apr 2019 15:44:21 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Kangjie Lu <kjlu@....edu>, Pablo Neira Ayuso <pablo@...filter.org>,
        Sasha Levin <sashal@...nel.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 13/68] netfilter: ip6t_srh: fix NULL pointer dereferences

From: Kangjie Lu <kjlu@....edu>

[ Upstream commit 6d65561f3d5ec933151939c543d006b79044e7a6 ]

skb_header_pointer may return NULL. The current code dereference
its return values without a NULL check.

The fix inserts the checks to avoid NULL pointer dereferences.

Fixes: 202a8ff545cc ("netfilter: add IPv6 segment routing header 'srh' match")
Signed-off-by: Kangjie Lu <kjlu@....edu>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Sasha Levin (Microsoft) <sashal@...nel.org>
---
 net/ipv6/netfilter/ip6t_srh.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv6/netfilter/ip6t_srh.c b/net/ipv6/netfilter/ip6t_srh.c
index 1059894a6f4c..4cb83fb69844 100644
--- a/net/ipv6/netfilter/ip6t_srh.c
+++ b/net/ipv6/netfilter/ip6t_srh.c
@@ -210,6 +210,8 @@ static bool srh1_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 		psidoff = srhoff + sizeof(struct ipv6_sr_hdr) +
 			  ((srh->segments_left + 1) * sizeof(struct in6_addr));
 		psid = skb_header_pointer(skb, psidoff, sizeof(_psid), &_psid);
+		if (!psid)
+			return false;
 		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_PSID,
 				ipv6_masked_addr_cmp(psid, &srhinfo->psid_msk,
 						     &srhinfo->psid_addr)))
@@ -223,6 +225,8 @@ static bool srh1_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 		nsidoff = srhoff + sizeof(struct ipv6_sr_hdr) +
 			  ((srh->segments_left - 1) * sizeof(struct in6_addr));
 		nsid = skb_header_pointer(skb, nsidoff, sizeof(_nsid), &_nsid);
+		if (!nsid)
+			return false;
 		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_NSID,
 				ipv6_masked_addr_cmp(nsid, &srhinfo->nsid_msk,
 						     &srhinfo->nsid_addr)))
@@ -233,6 +237,8 @@ static bool srh1_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 	if (srhinfo->mt_flags & IP6T_SRH_LSID) {
 		lsidoff = srhoff + sizeof(struct ipv6_sr_hdr);
 		lsid = skb_header_pointer(skb, lsidoff, sizeof(_lsid), &_lsid);
+		if (!lsid)
+			return false;
 		if (NF_SRH_INVF(srhinfo, IP6T_SRH_INV_LSID,
 				ipv6_masked_addr_cmp(lsid, &srhinfo->lsid_msk,
 						     &srhinfo->lsid_addr)))
-- 
2.19.1

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