netdev - Re: [PATCH 2/3] net: UDP gro

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+mtBx_+fc5YdQE+M49QD5ymuD7bfDdedfi2AuCDhU2=CawN6Q@mail.gmail.com>
Date:	Thu, 13 Feb 2014 14:27:54 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	Or Gerlitz <ogerlitz@...lanox.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Joseph Gasparakis <joseph.gasparakis@...el.com>,
	Jerry Chu <hkchu@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH 2/3] net: UDP gro_receive accept csum=0

> Hi Tom,
>
> Considering the patch just "as is" vs. the current code, its OK.
>
> However, as skbs have only one indicator for the status of the checksum
> checks done by the receiving hardware, the basic assertion I thought we
> needed here is to reject skb if either it has the udp mark set or the
> encapsulation field is false, this is according to the conventions set by
> these two commits
>
> 0afb166 vxlan: Add capability of Rx checksum offload for inner packet
> 6a674e9 net: Add support for hardware-offloaded encapsulation
>
> B/c after finalizing the GRO work and decapsulating, skb injected up into
> the TCP stack with ip_summed equals to CHECKSUM_NONE are rejected. If this
> assumption is wrong, maybe we can remove testing the ip_summed field here
> altogether?
>
If I'm interpreting the semantics correctly, when skb->encapsulation
is set the ip_summed is valid for both the inner and outer header
(e.g. CHECKSUM_COMPLETE is always assumed okay for both layers). If
skb->encapsulation is not set then ip_summed is only valid for outer
header. So then the patch is broken in the case that encap is not set,
ip_summed is CHECKSUM_UNNECESSARY, csum == 0, and we need to validate
the inner checksum.

But even worse, is there a fundamental issue where udp4_csum_init is
able to change ip_summed to be CHECKSUM_UNNECESSARY (either check == 0
or ip_summed == CHECKSUM_UNNECESSARY) regardless of
skb->encapsulation, sending the packet into encap_rcv which could
ultimately incorrectly apply ip_summed on the inner TCP/UDP packet?

Tom

> Or.
>
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html