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

[Saeed Mirzamohammadi]

Attached the syzkaller C repro.

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

Attachment: repro.c
Description: Binary data

> On Oct 20, 2020, at 9:45 AM, Saeed Mirzamohammadi <saeed.mirzamohammadi@xxxxxxxxxx> wrote:
> 
> Thanks! Yes, that looks good to me.
> 
> Saeed
> 
>> On Oct 20, 2020, at 4:50 AM, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote:
>> 
>> On Mon, Oct 19, 2020 at 10:25:32AM -0700, saeed.mirzamohammadi@xxxxxxxxxx wrote:
>>> From: Saeed Mirzamohammadi <saeed.mirzamohammadi@xxxxxxxxxx>
>>> 
>>> 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>
>