netdev - Re: [PATCH linux-5.9 1/1] net: netfilter: fix KASAN: slab-out-of-bounds Read in nft_flow_rule

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Date:   Wed, 21 Oct 2020 13:08:24 -0700
From:   Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
To:     Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, kadlec@...filter.org, fw@...len.de,
        davem@...emloft.net, kuba@...nel.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH linux-5.9 1/1] net: netfilter: fix KASAN:
 slab-out-of-bounds Read in nft_flow_rule_create

Attached the syzkaller C repro.

Tested-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>

Download attachment "repro.c" of type "application/octet-stream" (5052 bytes)


> On Oct 20, 2020, at 9:45 AM, Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com> wrote:
> 
> Thanks! Yes, that looks good to me.
> 
> Saeed
> 
>> On Oct 20, 2020, at 4:50 AM, Pablo Neira Ayuso <pablo@...filter.org> wrote:
>> 
>> On Mon, Oct 19, 2020 at 10:25:32AM -0700, saeed.mirzamohammadi@...cle.com wrote:
>>> From: Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
>>> 
>>> This patch fixes the issue due to:
>>> 
>>> BUG: KASAN: slab-out-of-bounds in nft_flow_rule_create+0x622/0x6a2
>>> net/netfilter/nf_tables_offload.c:40
>>> Read of size 8 at addr ffff888103910b58 by task syz-executor227/16244
>>> 
>>> The error happens when expr->ops is accessed early on before performing the boundary check and after nft_expr_next() moves the expr to go out-of-bounds.
>>> 
>>> This patch checks the boundary condition before expr->ops that fixes the slab-out-of-bounds Read issue.
>> 
>> Thanks. I made a slight variant of your patch.
>> 
>> I'm attaching it, it is also fixing the problem but it introduced
>> nft_expr_more() and use it everywhere.
>> 
>> Let me know if this looks fine to you.
>> <0001-netfilter-fix-KASAN-slab-out-of-bounds-Read-in-nft_f.patch>
>