Subject: Re: [PATCH] net: ipmr: limit MRT_TABLE identifiers

From: Chen Gang <[email-masked]>
Date: Mon, 26 Nov 2012 09:34:39 +0800

于 2012年11月26日 09:22, Chen Gang 写道:
> 于 2012年11月26日 03:44, Eric Dumazet 写道:
>> From: Eric Dumazet <[email-masked]>
>>
>> Name of pimreg devices are built from following format :
>>
>> char name[IFNAMSIZ]; // IFNAMSIZ == 16
>>
>> sprintf(name, "pimreg%u", mrt->id);
>>
>> We must therefore limit mrt->id to 9 decimal digits
>> or risk a buffer overflow and a crash.
>>
>> Restrict table identifiers in [0 ... 999999999] interval.
>>

    if "pimre%u" (or another format), will not hurt the functional features, I suggest to use it
      since, we need try our best to not touch the OS API. 
      ("pimreg%u" seems an internal format, not OS API Level)

> 
>   if we have to stick to "pimreg%u" (or will hurt the functional features)
>   suggest to let user mode know this limitation. 
>     define a macro in public header (user mode can know it) and give comments.
>     use macro instead of number.
>     remove the comments which is inside internal function.
> 
>   thanks.
> 
> gchen.
> 
> 
>> Reported-by: Chen Gang <[email-masked]>
>> Signed-off-by: Eric Dumazet <[email-masked]>
>> ---
>>  net/ipv4/ipmr.c |    4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
>> index 6168c4d..3eab2b2 100644
>> --- a/net/ipv4/ipmr.c
>> +++ b/net/ipv4/ipmr.c
>> @@ -1318,6 +1318,10 @@ int ip_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, unsi
>>  		if (get_user(v, (u32 __user *)optval))
>>  			return -EFAULT;
>>  
>> +		/* "pimreg%u" should not exceed 16 bytes (IFNAMSIZ) */
>> +		if (v != RT_TABLE_DEFAULT && v >= 1000000000)
>> +			return -EINVAL;
>> +
>>  		rtnl_lock();
>>  		ret = 0;
>>  		if (sk == rtnl_dereference(mrt->mroute_sk)) {
>>
>>
>>
>>
> 
> 

-- 
Chen Gang

Asianux Corporation