netdev - Re: [PATCH net] net: fix possible out-of-bound read in skb_network

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Message-Id: <20180327.105359.1310806514333543510.davem@davemloft.net>
Date:   Tue, 27 Mar 2018 10:53:59 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com, pshelar@....org
Subject: Re: [PATCH net] net: fix possible out-of-bound read in
 skb_network_protocol()

From: Eric Dumazet <edumazet@...gle.com>
Date: Mon, 26 Mar 2018 08:08:07 -0700

> skb mac header is not necessarily set at the time skb_network_protocol()
> is called. Use skb->data instead.
> 
> BUG: KASAN: slab-out-of-bounds in skb_network_protocol+0x46b/0x4b0 net/core/dev.c:2739
> Read of size 2 at addr ffff8801b3097a0b by task syz-executor5/14242
> 
> CPU: 1 PID: 14242 Comm: syz-executor5 Not tainted 4.16.0-rc6+ #280
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x24d lib/dump_stack.c:53
>  print_address_description+0x73/0x250 mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report+0x23c/0x360 mm/kasan/report.c:412
>  __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:443
>  skb_network_protocol+0x46b/0x4b0 net/core/dev.c:2739
>  harmonize_features net/core/dev.c:2924 [inline]
>  netif_skb_features+0x509/0x9b0 net/core/dev.c:3011
>  validate_xmit_skb+0x81/0xb00 net/core/dev.c:3084
>  validate_xmit_skb_list+0xbf/0x120 net/core/dev.c:3142
>  packet_direct_xmit+0x117/0x790 net/packet/af_packet.c:256
>  packet_snd net/packet/af_packet.c:2944 [inline]
>  packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2969
>  sock_sendmsg_nosec net/socket.c:629 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:639
>  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
>  __sys_sendmsg+0xe5/0x210 net/socket.c:2081
> 
> Fixes: 19acc327258a ("gso: Handle Trans-Ether-Bridging protocol in skb_network_protocol()")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Pravin B Shelar <pshelar@....org>
> Reported-by: Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable, thanks Eric.