From: walter harms <wharms@bfs.de>
To: kernel-janitors@vger.kernel.org
Subject: Re: [PATCH 1/3] netfilter: Fix copy_to_user too small size parametre.
Date: Thu, 01 Mar 2012 15:00:03 +0000 [thread overview]
Message-ID: <4F4F8EF3.3040102@bfs.de> (raw)
In-Reply-To: <1330593390-19233-1-git-send-email-santoshprasadnayak@gmail.com>
Am 01.03.2012 14:03, schrieb Pablo Neira Ayuso:
> On Thu, Mar 01, 2012 at 04:15:05PM +0530, santosh prasad nayak wrote:
>> Hi Pablo.
>>
>> copy_to_user( dest, source, length)
>>
>> Normally, 'length' is equal to 'sizeof (source) '.
>>
>> In this case "length" = 32
>> "sizeof(source)" = 29.
>>
>> Is it intentional ?
>
> ebtables expects 32 bytes names.
>
>> Won't it copy extra 3 bytes of kernel data to userspace ?
>
> You're right. We have to copy 29 bytes but we have to fill the
> remaining bytes with zeroes. I think something like:
>
> char name[EBT_FUNCTION_MAXNAMELEN] = {};
>
> /* user-space ebtables expects 32 bytes-long names, but xt_match uses
> * 29 bytes for that. */
> sprintf(name, "%s", m->u.match->name);
> if (copy_to_user(hlp, name, EBT_FUNCTION_MAXNAMELEN))
> ...
>
it may be better to use kstrncpy() here. kstrncpy will fill remaining
space with 0. now you are using char name[EBT_FUNCTION_MAXNAMELEN] later
this may change, better safe than sorry.
re,
wh
> will resolve this issue.
>
> Would you resend a new patch?
> --
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prev parent reply other threads:[~2012-03-01 15:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-01 9:28 [PATCH 1/3] netfilter: Fix copy_to_user too small size parametre santosh nayak
2012-03-01 10:18 ` Pablo Neira Ayuso
2012-03-01 10:57 ` santosh prasad nayak
2012-03-01 13:03 ` Pablo Neira Ayuso
2012-03-01 13:52 ` santosh prasad nayak
2012-03-01 11:37 ` Dan Carpenter
2012-03-01 13:06 ` Pablo Neira Ayuso
2012-03-01 13:13 ` Dan Carpenter
2012-03-01 11:31 ` Dan Carpenter
2012-03-01 15:00 ` walter harms [this message]
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