[PATCH] IPVS: replace sprintf to snprintf to avoid stack buffer overflow

[wzt.wzt@xxxxxxxxx]

IPVS not check the length of pp->name, use sprintf will cause stack buffer 
overflow.
struct ip_vs_protocol{} declare name as char *, if register a protocol as:
struct ip_vs_protocol ip_vs_test = {
        .name =                 "aaaaaaaa....128...aaa",
        .debug_packet =         ip_vs_tcpudp_debug_packet,
};

when called ip_vs_tcpudp_debug_packet(), sprintf(buf, "%s TRUNCATED", 
pp->name); 
will cause stack buffer overflow.

Signed-off-by: Zhitong Wang <zhitong.wangzt@xxxxxxxxxxxxxxx>

---
 net/netfilter/ipvs/ip_vs_proto.c        |   16 ++++++++--------
 net/netfilter/ipvs/ip_vs_proto_ah_esp.c |    8 ++++----
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_proto.c b/net/netfilter/ipvs/ip_vs_proto.c
index 0e58455..8143318 100644
--- a/net/netfilter/ipvs/ip_vs_proto.c
+++ b/net/netfilter/ipvs/ip_vs_proto.c
@@ -166,9 +166,9 @@ 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);
+               snprintf(buf, sizeof(buf), "%s TRUNCATED", pp->name);
        else if (ih->frag_off & htons(IP_OFFSET))
-               sprintf(buf, "%s %pI4->%pI4 frag",
+               snprintf(buf, sizeof(buf), "%s %pI4->%pI4 frag",
                        pp->name, &ih->saddr, &ih->daddr);
        else {
                __be16 _ports[2], *pptr
@@ -176,10 +176,10 @@ ip_vs_tcpudp_debug_packet_v4(struct ip_vs_protocol *pp,
                pptr = skb_header_pointer(skb, offset + ih->ihl*4,
                                          sizeof(_ports), _ports);
                if (pptr == NULL)
-                       sprintf(buf, "%s TRUNCATED %pI4->%pI4",
+                       snprintf(buf, sizeof(buf), "%s TRUNCATED %pI4->%pI4",
                                pp->name, &ih->saddr, &ih->daddr);
                else
-                       sprintf(buf, "%s %pI4:%u->%pI4:%u",
+                       snprintf(buf, sizeof(buf), "%s %pI4:%u->%pI4:%u",
                                pp->name,
                                &ih->saddr, ntohs(pptr[0]),
                                &ih->daddr, ntohs(pptr[1]));
@@ -200,9 +200,9 @@ 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);
+               snprintf(buf, sizeof(buf), "%s TRUNCATED", pp->name);
        else if (ih->nexthdr == IPPROTO_FRAGMENT)
-               sprintf(buf, "%s %pI6->%pI6 frag",
+               snprintf(buf, sizeof(buf), "%s %pI6->%pI6 frag",
                        pp->name, &ih->saddr, &ih->daddr);
        else {
                __be16 _ports[2], *pptr;
@@ -210,10 +210,10 @@ ip_vs_tcpudp_debug_packet_v6(struct ip_vs_protocol *pp,
                pptr = skb_header_pointer(skb, offset + sizeof(struct ipv6hdr),
                                          sizeof(_ports), _ports);
                if (pptr == NULL)
-                       sprintf(buf, "%s TRUNCATED %pI6->%pI6",
+                       snprintf(buf, sizeof(buf), "%s TRUNCATED %pI6->%pI6",
                                pp->name, &ih->saddr, &ih->daddr);
                else
-                       sprintf(buf, "%s %pI6:%u->%pI6:%u",
+                       snprintf(buf, sizeof(buf), "%s %pI6:%u->%pI6:%u",
                                pp->name,
                                &ih->saddr, ntohs(pptr[0]),
                                &ih->daddr, ntohs(pptr[1]));
diff --git a/net/netfilter/ipvs/ip_vs_proto_ah_esp.c 
b/net/netfilter/ipvs/ip_vs_proto_ah_esp.c
index c30b43c..ce795ab 100644
--- a/net/netfilter/ipvs/ip_vs_proto_ah_esp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_ah_esp.c
@@ -136,9 +136,9 @@ 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);
+               snprintf(buf, sizeof(buf), "%s TRUNCATED", pp->name);
        else
-               sprintf(buf, "%s %pI4->%pI4",
+               snprintf(buf, sizeof(buf), "%s %pI4->%pI4",
                        pp->name, &ih->saddr, &ih->daddr);
 
        pr_debug("%s: %s\n", msg, buf);
@@ -154,9 +154,9 @@ 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);
+               snprintf(buf, sizeof(buf), "%s TRUNCATED", pp->name);
        else
-               sprintf(buf, "%s %pI6->%pI6",
+               snprintf(buf, sizeof(buf), "%s %pI6->%pI6",
                        pp->name, &ih->saddr, &ih->daddr);
 
        pr_debug("%s: %s\n", msg, buf);
-- 
1.6.5.3

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