Re: [PATCH] flow disector: check if arp_eth is null rather than arp

[Eric Dumazet]

On Fri, 2017-01-13 at 18:25 +, Colin Ian King wrote:
> On 13/01/17 18:24, Eric Dumazet wrote:

> > It looks that we try very hard to add critical bugs in flow dissector.
> > 
> > This is embarrassing really.
> > 
> > I am questioning if the __skb_header_pointer() is correct
> > 
> > Why using hlen - sizeof(_arp) ?
> > 
> >arp_eth = __skb_header_pointer(skb, nhoff + sizeof(_arp),
> >   sizeof(_arp_eth), data,
> >   hlen - sizeof(_arp),
> >   &_arp_eth);
> > 
> 
> Yep, the sizeof maybe dubious too, I overlooked that one; if somebody
> can clarify that then I'll send a V2 if it needs fixing up too.

I am pretty sure we should use hlen instead of (hlen - sizeof(_arp))

A V2 would be nice ;)

Re: [PATCH] flow disector: check if arp_eth is null rather than arp

[Eric Dumazet]

On Fri, 2017-01-13 at 13:34 +, Colin King wrote:
> From: Colin Ian King 
> 
> arp is being checked instead of arp_eth to see if the call to
> __skb_header_pointer failed. Fix this by checking arp_eth is
> null instead of arp.
> 
> CoverityScan CID#1396428 ("Logically dead code") on 2nd
> arp comparison (which should be arp_eth instead).
> 
> Fixes: commit 55733350e5e8b70c5 ("flow disector: ARP support")
> Signed-off-by: Colin Ian King 
> ---
>  net/core/flow_dissector.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index e3dffc7..fec48e9 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -409,7 +409,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>  sizeof(_arp_eth), data,
>  hlen - sizeof(_arp),
>  &_arp_eth);
> - if (!arp)
> + if (!arp_eth)
>   goto out_bad;
>  
>   if (dissector_uses_key(flow_dissector,

It looks that we try very hard to add critical bugs in flow dissector.

This is embarrassing really.

I am questioning if the __skb_header_pointer() is correct

Why using hlen - sizeof(_arp) ?

   arp_eth = __skb_header_pointer(skb, nhoff + sizeof(_arp),
  sizeof(_arp_eth), data,
  hlen - sizeof(_arp),
  &_arp_eth);

Re: [PATCH] flow disector: check if arp_eth is null rather than arp

[Colin Ian King]

On 13/01/17 18:24, Eric Dumazet wrote:
> On Fri, 2017-01-13 at 13:34 +, Colin King wrote:
>> From: Colin Ian King 
>>
>> arp is being checked instead of arp_eth to see if the call to
>> __skb_header_pointer failed. Fix this by checking arp_eth is
>> null instead of arp.
>>
>> CoverityScan CID#1396428 ("Logically dead code") on 2nd
>> arp comparison (which should be arp_eth instead).
>>
>> Fixes: commit 55733350e5e8b70c5 ("flow disector: ARP support")
>> Signed-off-by: Colin Ian King 
>> ---
>>  net/core/flow_dissector.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>> index e3dffc7..fec48e9 100644
>> --- a/net/core/flow_dissector.c
>> +++ b/net/core/flow_dissector.c
>> @@ -409,7 +409,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>> sizeof(_arp_eth), data,
>> hlen - sizeof(_arp),
>> &_arp_eth);
>> -if (!arp)
>> +if (!arp_eth)
>>  goto out_bad;
>>  
>>  if (dissector_uses_key(flow_dissector,
> 
> It looks that we try very hard to add critical bugs in flow dissector.
> 
> This is embarrassing really.
> 
> I am questioning if the __skb_header_pointer() is correct
> 
> Why using hlen - sizeof(_arp) ?
> 
>arp_eth = __skb_header_pointer(skb, nhoff + sizeof(_arp),
>   sizeof(_arp_eth), data,
>   hlen - sizeof(_arp),
>   &_arp_eth);
> 

Yep, the sizeof maybe dubious too, I overlooked that one; if somebody
can clarify that then I'll send a V2 if it needs fixing up too.

Colin

[PATCH] flow disector: check if arp_eth is null rather than arp

[Colin King]

From: Colin Ian King 

arp is being checked instead of arp_eth to see if the call to
__skb_header_pointer failed. Fix this by checking arp_eth is
null instead of arp.

CoverityScan CID#1396428 ("Logically dead code") on 2nd
arp comparison (which should be arp_eth instead).

Fixes: commit 55733350e5e8b70c5 ("flow disector: ARP support")
Signed-off-by: Colin Ian King 
---
 net/core/flow_dissector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index e3dffc7..fec48e9 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -409,7 +409,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
   sizeof(_arp_eth), data,
   hlen - sizeof(_arp),
   &_arp_eth);
-   if (!arp)
+   if (!arp_eth)
goto out_bad;
 
if (dissector_uses_key(flow_dissector,
-- 
2.10.2