IPVS: fix potential stack overflow with overly long protocol names

When protocols use very long names, the sprintf calls might overflow
the on-stack buffer. No protocol in the kernel does this however.

Print the protocol name in the pr_debug statement directly to avoid
this.

Based on patch by Zhitong Wang <zhitong.wangzt@alibaba-inc.com>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Patrick McHardy <kaber@trash.net>

2 files changed, 18 insertions, 24 deletions

diff --git a/net/netfilter/ipvs/ip_vs_proto.c b/net/netfilter/ipvs/ip_vs_proto.c
index 0e584553819d..27add971bb13 100644
--- a/net/netfilter/ipvs/ip_vs_proto.c
+++ b/net/netfilter/ipvs/ip_vs_proto.c
@@ -166,26 +166,24 @@ ip_vs_tcpudp_debug_packet_v4(struct ip_vs_protocol *pp,
 
         ih = skb_header_pointer(skb, offset, sizeof(_iph), &_iph);
         if (ih == NULL)
-                sprintf(buf, "%s TRUNCATED", pp->name);
+                sprintf(buf, "TRUNCATED");
         else if (ih->frag_off & htons(IP_OFFSET))
-                sprintf(buf, "%s %pI4->%pI4 frag",
-                        pp->name, &ih->saddr, &ih->daddr);
+                sprintf(buf, "%pI4->%pI4 frag", &ih->saddr, &ih->daddr);
         else {
                 __be16 _ports[2], *pptr
 ;
                 pptr = skb_header_pointer(skb, offset + ih->ihl*4,
                                           sizeof(_ports), _ports);
                 if (pptr == NULL)
-                        sprintf(buf, "%s TRUNCATED %pI4->%pI4",
-                                pp->name, &ih->saddr, &ih->daddr);
+                        sprintf(buf, "TRUNCATED %pI4->%pI4",
+                                &ih->saddr, &ih->daddr);
                 else
-                        sprintf(buf, "%s %pI4:%u->%pI4:%u",
-                                pp->name,
+                        sprintf(buf, "%pI4:%u->%pI4:%u",
                                 &ih->saddr, ntohs(pptr[0]),
                                 &ih->daddr, ntohs(pptr[1]));
         }
 
-        pr_debug("%s: %s\n", msg, buf);
+        pr_debug("%s: %s %s\n", msg, pp->name, buf);
 }
 
 #ifdef CONFIG_IP_VS_IPV6
@@ -200,26 +198,24 @@ ip_vs_tcpudp_debug_packet_v6(struct ip_vs_protocol *pp,
 
         ih = skb_header_pointer(skb, offset, sizeof(_iph), &_iph);
         if (ih == NULL)
-                sprintf(buf, "%s TRUNCATED", pp->name);
+                sprintf(buf, "TRUNCATED");
         else if (ih->nexthdr == IPPROTO_FRAGMENT)
-                sprintf(buf, "%s %pI6->%pI6 frag",
-                        pp->name, &ih->saddr, &ih->daddr);
+                sprintf(buf, "%pI6->%pI6 frag", &ih->saddr, &ih->daddr);
         else {
                 __be16 _ports[2], *pptr;
 
                 pptr = skb_header_pointer(skb, offset + sizeof(struct ipv6hdr),
                                           sizeof(_ports), _ports);
                 if (pptr == NULL)
-                        sprintf(buf, "%s TRUNCATED %pI6->%pI6",
-                                pp->name, &ih->saddr, &ih->daddr);
+                        sprintf(buf, "TRUNCATED %pI6->%pI6",
+                                &ih->saddr, &ih->daddr);
                 else
-                        sprintf(buf, "%s %pI6:%u->%pI6:%u",
-                                pp->name,
+                        sprintf(buf, "%pI6:%u->%pI6:%u",
                                 &ih->saddr, ntohs(pptr[0]),
                                 &ih->daddr, ntohs(pptr[1]));
         }
 
-        pr_debug("%s: %s\n", msg, buf);
+        pr_debug("%s: %s %s\n", msg, pp->name, buf);
 }
 #endif
 
diff --git a/net/netfilter/ipvs/ip_vs_proto_ah_esp.c b/net/netfilter/ipvs/ip_vs_proto_ah_esp.c
index c30b43c36cd7..1892dfc12fdd 100644
--- a/net/netfilter/ipvs/ip_vs_proto_ah_esp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_ah_esp.c
@@ -136,12 +136,11 @@ ah_esp_debug_packet_v4(struct ip_vs_protocol *pp, const struct sk_buff *skb,
 
         ih = skb_header_pointer(skb, offset, sizeof(_iph), &_iph);
         if (ih == NULL)
-                sprintf(buf, "%s TRUNCATED", pp->name);
+                sprintf(buf, "TRUNCATED");
         else
-                sprintf(buf, "%s %pI4->%pI4",
-                        pp->name, &ih->saddr, &ih->daddr);
+                sprintf(buf, "%pI4->%pI4", &ih->saddr, &ih->daddr);
 
-        pr_debug("%s: %s\n", msg, buf);
+        pr_debug("%s: %s %s\n", msg, pp->name, buf);
 }
 
 #ifdef CONFIG_IP_VS_IPV6
@@ -154,12 +153,11 @@ ah_esp_debug_packet_v6(struct ip_vs_protocol *pp, const struct sk_buff *skb,
 
         ih = skb_header_pointer(skb, offset, sizeof(_iph), &_iph);
         if (ih == NULL)
-                sprintf(buf, "%s TRUNCATED", pp->name);
+                sprintf(buf, "TRUNCATED");
         else
-                sprintf(buf, "%s %pI6->%pI6",
-                        pp->name, &ih->saddr, &ih->daddr);
+                sprintf(buf, "%pI6->%pI6", &ih->saddr, &ih->daddr);
 
-        pr_debug("%s: %s\n", msg, buf);
+        pr_debug("%s: %s %s\n", msg, pp->name, buf);
 }
 #endif