netdev - Re: [PATCH net-next] net: fix use-after-free in kfree_skb

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Message-ID: <20190603090727.g2cxedtuwe2hhvjl@salvia>
Date:   Mon, 3 Jun 2019 11:07:27 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next] net: fix use-after-free in kfree_skb_list

On Sun, Jun 02, 2019 at 11:24:18AM -0700, Eric Dumazet wrote:
> syzbot reported nasty use-after-free [1]
> 
> Lets remove frag_list field from structs ip_fraglist_iter
> and ip6_fraglist_iter. This seens not needed anyway.
> 
> [1] :
> BUG: KASAN: use-after-free in kfree_skb_list+0x5d/0x60 net/core/skbuff.c:706
> Read of size 8 at addr ffff888085a3cbc0 by task syz-executor303/8947
[...]
> 
> Memory state around the buggy address:
>  ffff888085a3ca80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff888085a3cb00: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
> >ffff888085a3cb80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>                                            ^
>  ffff888085a3cc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888085a3cc80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
> 
> Fixes: 0feca6190f88 ("net: ipv6: add skbuff fraglist splitter")
> Fixes: c8b17be0b7a4 ("net: ipv4: add skbuff fraglist splitter")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Pablo Neira Ayuso <pablo@...filter.org>

Acked-by: Pablo Neira Ayuso <pablo@...filter.org>

Thanks!