linux-kernel - Re: [PATCH v2 net-next] fix unsafe set_memory

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Message-ID: <CAMEtUuxABV2sRjW=azWj7k80O3cig_zh3CgAzKdTSi4rtCrGLg@mail.gmail.com>
Date:	Thu, 3 Oct 2013 19:26:33 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Xi Wang <xi.wang@...il.com>, x86@...nel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next] fix unsafe set_memory_rw from softirq

On Thu, Oct 3, 2013 at 4:11 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
> On Thu, Oct 3, 2013 at 4:07 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> On Thu, 2013-10-03 at 15:47 -0700, Alexei Starovoitov wrote:
>>
>>> @@ -722,7 +725,8 @@ EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy);
>>>  int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
>>>  {
>>>       struct sk_filter *fp, *old_fp;
>>> -     unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
>>> +     unsigned int fsize = max(sizeof(struct sock_filter) * fprog->len,
>>> +                              sizeof(struct work_struct));
>>>       int err;
>>>
>>>       if (sock_flag(sk, SOCK_FILTER_LOCKED))
>>
>> Thats broken, as we might copy more data from user than expected,
>> and eventually trigger EFAULT :
>>
>> if (copy_from_user(fp->insns, fprog->filter, fsize)) {
>
> yes. will fix.

tested on x86_64/i386 only
with tcpdump and netsniff 1-4k filter size.
Thank you for careful review.
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