netfilter: ip6t_srh: fix NULL pointer dereferences

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@umn.edu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv6/netfilter/ip6t_srh.c b/net/ipv6/netfilter/ip6t_srh.c
index 1059894..4cb83fb 100644 (file)
--- 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)))