netdev - Re: Resend [PATCH] netfilter: Fix copy_to

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Message-ID: <CAOD=uF6UvL2oEmJmgak4X5L0PR+qQi2=Vr22AUsAxLLOfi44rw@mail.gmail.com>
Date:	Sun, 4 Mar 2012 18:09:08 +0530
From:	santosh prasad nayak <santoshprasadnayak@...il.com>
To:	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	bart.de.schuymer@...dora.be, kaber@...sh.net,
	shemminger@...tta.com, davem@...emloft.net, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: Resend [PATCH] netfilter: Fix copy_to_user too small size parametre.

where is it broken ?
Can you please explain ?

Regards
Santosh

On Sun, Mar 4, 2012 at 5:48 PM, Pablo Neira Ayuso <pablo@...filter.org> wrote:
> On Thu, Mar 01, 2012 at 10:39:03PM +0530, santosh nayak wrote:
>> From: Santosh Nayak <santoshprasadnayak@...il.com>
>>
>> user-space ebtables expects 32 bytes-long names, but xt_match uses
>> 29 bytes. Fill the remaining bytes with zeroes.
>>
>> Signed-off-by: Santosh Nayak <santoshprasadnayak@...il.com>
>> ---
>>  net/bridge/netfilter/ebtables.c |   14 +++++++++++---
>>  1 files changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
>> index 5864cc4..21f337a 100644
>> --- a/net/bridge/netfilter/ebtables.c
>> +++ b/net/bridge/netfilter/ebtables.c
>> @@ -1335,7 +1335,10 @@ static inline int ebt_make_matchname(const struct ebt_entry_match *m,
>>      const char *base, char __user *ubase)
>>  {
>>       char __user *hlp = ubase + ((char *)m - base);
>> -     if (copy_to_user(hlp, m->u.match->name, EBT_FUNCTION_MAXNAMELEN))
>> +     char name[EBT_FUNCTION_MAXNAMELEN] = {};
>> +
>> +     strncpy(name, m->u.match->name, sizeof(name));
>> +     if (copy_to_user(hlp, name, EBT_FUNCTION_MAXNAMELEN))
>>               return -EFAULT;
>>       return 0;
>>  }
>> @@ -1344,7 +1347,10 @@ static inline int ebt_make_watchername(const struct ebt_entry_watcher *w,
>>      const char *base, char __user *ubase)
>>  {
>>       char __user *hlp = ubase + ((char *)w - base);
>> -     if (copy_to_user(hlp , w->u.watcher->name, EBT_FUNCTION_MAXNAMELEN))
>> +     char name[EBT_FUNCTION_MAXNAMELEN] = {};
>> +
>> +     strncpy(name, w->u.watcher->name, sizeof(name));
>> +     if (copy_to_user(hlp , name, EBT_FUNCTION_MAXNAMELEN))
>>               return -EFAULT;
>>       return 0;
>>  }
>> @@ -1355,10 +1361,12 @@ ebt_make_names(struct ebt_entry *e, const char *base, char __user *ubase)
>>       int ret;
>>       char __user *hlp;
>>       const struct ebt_entry_target *t;
>> +     char name[EBT_FUNCTION_MAXNAMELEN] = {};
>>
>>       if (e->bitmask == 0)
>>               return 0;
>>
>> +     strncpy(name, t->u.target->name, sizeof(name));
>>       hlp = ubase + (((char *)e + e->target_offset) - base);
>>       t = (struct ebt_entry_target *)(((char *)e) + e->target_offset);
>
> This is broken, t dereference is incorrect. Unfortunately I've applied
> your patch. I'll apply a patch to fix this upon it.
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