netdev - Re: [PATCH RFC net-next] packet: always ensure that we pass hard_header_len bytes in skb

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]

Date:   Fri, 27 Jan 2017 10:28:16 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:     David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH RFC net-next] packet: always ensure that we pass
 hard_header_len bytes in skb_headlen() to the driver

> " The AX.25 device level drivers are simply written to be robust if
>   thrown partial frames.
>    :
>   The other thing that concerns me about this added logic in general is
>   that you are also breaking test tools that want to deliberately send
>   corrupt frames to certain classes of interface."
>
> But how does the driver (even a robust one!) compute the L2 dst/src if the
> application has not even passed down the minimum (which is 21 for ax25?)

Perhaps the goal is to test that the driver gracefully handles such
packets. I can only speculate.

> Would it make sense to only do the CAP_SYS_RAWIO branch if the
> driver declares itself to have variable length L2 headers, via, e.g.,
> some priv flag?

At the time, the comments were not specific to AX25. Again, we should
probably put that bypass behind a flag, enabling validating in the common case.

> BTW the http://comments.gmane.org/gmane.linux.network/401064 referred
> to in commit 2793a23 is not accessible any more, not sure if its contents
> were the same as the link you just shared.

It is. I looked it up in my email archive. Too bad that that seems to
be the only way.