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

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

[wzt.wzt]

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@alibaba-inc.com>

---
 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

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

[Changli Gao]

On Tue, Apr 6, 2010 at 10:50 AM,  <wzt.wzt@gmail.com> wrote:
> 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.
>

Long messages will be truncated instead of buffer overflow. We need to
find a way to handle long messages elegantly.

-- 
Regards，
Changli Gao(xiaosuo@gmail.com)

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

[Changli Gao]

On Tue, Apr 6, 2010 at 10:50 AM,  <wzt.wzt@gmail.com> wrote:
> 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.
>

Long messages will be truncated instead of buffer overflow. We need to
find a way to handle long messages elegantly.

-- 
Regards，
Changli Gao(xiaosuo@gmail.com)

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

[Simon Horman]

On Tue, Apr 06, 2010 at 10:50:20AM +0800, wzt.wzt@gmail.com wrote:
> 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@alibaba-inc.com>

I think that the simple answer is, don't do that.
But your patch seems entirely reasonable to me.

Acked-by: Simon Horman <horms@verge.net.au>

Patrick, please consider merging this.

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

[Simon Horman]

On Tue, Apr 06, 2010 at 10:58:28AM +0800, Changli Gao wrote:
> On Tue, Apr 6, 2010 at 10:50 AM,  <wzt.wzt@gmail.com> wrote:
> > 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.
> >
> 
> Long messages will be truncated instead of buffer overflow. We need to
> find a way to handle long messages elegantly.

Its really a corner case. In practice protocol modules don't have really
long names. And if one was merged that did, the buffer size could be increased
at that time.

So while I think its reasonable to protect against something unexpected
in a protocol-module name crashing the system. Especially as that
can be achieved without any real overhead. I don't think we need
to sanitise the output.

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

[Patrick McHardy]

[-- Attachment #1: Type: text/plain, Size: 968 bytes --]

Simon Horman wrote:
> On Tue, Apr 06, 2010 at 10:50:20AM +0800, wzt.wzt@gmail.com wrote:
>> 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@alibaba-inc.com>
> 
> I think that the simple answer is, don't do that.

Indeed.

> But your patch seems entirely reasonable to me.
> 
> Acked-by: Simon Horman <horms@verge.net.au>
> 
> Patrick, please consider merging this.

I think this fix is a bit silly, we can simply print the name in
the pr_debug() statement and avoid both the potential overflow
and truncation.

How does this look?

[-- Attachment #2: x --]
[-- Type: text/plain, Size: 3385 bytes --]

diff --git a/net/netfilter/ipvs/ip_vs_proto.c b/net/netfilter/ipvs/ip_vs_proto.c
index 0e58455..27add97 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 c30b43c..1892dfc 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
 

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

[Simon Horman]

On Wed, Apr 07, 2010 at 06:09:54PM +0200, Patrick McHardy wrote:
> Simon Horman wrote:
> > On Tue, Apr 06, 2010 at 10:50:20AM +0800, wzt.wzt@gmail.com wrote:
> >> 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@alibaba-inc.com>
> > 
> > I think that the simple answer is, don't do that.
> 
> Indeed.
> 
> > But your patch seems entirely reasonable to me.
> > 
> > Acked-by: Simon Horman <horms@verge.net.au>
> > 
> > Patrick, please consider merging this.
> 
> I think this fix is a bit silly, we can simply print the name in
> the pr_debug() statement and avoid both the potential overflow
> and truncation.
> 
> How does this look?

Looks good to me:

Acked-by: Simon Horman <horms@verge.net.au>

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

[Patrick McHardy]

Simon Horman wrote:
> On Wed, Apr 07, 2010 at 06:09:54PM +0200, Patrick McHardy wrote:
>> Simon Horman wrote:
>>> On Tue, Apr 06, 2010 at 10:50:20AM +0800, wzt.wzt@gmail.com wrote:
>>>> 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@alibaba-inc.com>
>>> I think that the simple answer is, don't do that.
>> Indeed.
>>
>>> But your patch seems entirely reasonable to me.
>>>
>>> Acked-by: Simon Horman <horms@verge.net.au>
>>>
>>> Patrick, please consider merging this.
>> I think this fix is a bit silly, we can simply print the name in
>> the pr_debug() statement and avoid both the potential overflow
>> and truncation.
>>
>> How does this look?
> 
> Looks good to me:
> 
> Acked-by: Simon Horman <horms@verge.net.au>

Thanks, I've applied the patch.