netdev - Re: [PATCH net] tunnels: fix out of bounds access when building IPv6 PMTU error

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Message-ID: <ZbuSWVur9iOYXp2v@nanopsycho>
Date: Thu, 1 Feb 2024 13:45:13 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Antoine Tenart <atenart@...nel.org>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
	edumazet@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] tunnels: fix out of bounds access when building IPv6
 PMTU error

Thu, Feb 01, 2024 at 09:38:15AM CET, atenart@...nel.org wrote:
>If the ICMPv6 error is built from a non-linear skb we get the following
>splat,
>
>  BUG: KASAN: slab-out-of-bounds in do_csum+0x220/0x240
>  Read of size 4 at addr ffff88811d402c80 by task netperf/820
>  CPU: 0 PID: 820 Comm: netperf Not tainted 6.8.0-rc1+ #543
>  ...
>   kasan_report+0xd8/0x110
>   do_csum+0x220/0x240
>   csum_partial+0xc/0x20
>   skb_tunnel_check_pmtu+0xeb9/0x3280
>   vxlan_xmit_one+0x14c2/0x4080
>   vxlan_xmit+0xf61/0x5c00
>   dev_hard_start_xmit+0xfb/0x510
>   __dev_queue_xmit+0x7cd/0x32a0
>   br_dev_queue_push_xmit+0x39d/0x6a0
>
>Use skb_checksum instead of csum_partial who cannot deal with non-linear
>SKBs.
>
>Fixes: 4cb47a8644cc ("tunnels: PMTU discovery support for directly bridged IP packets")
>Signed-off-by: Antoine Tenart <atenart@...nel.org>

Reviewed-by: Jiri Pirko <jiri@...dia.com>