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  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:	Tue, 11 Dec 2012 15:04:20 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	ani@...stanetworks.com
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Michael Richardson <mcr@...delman.ca>, netdev@...r.kernel.org,
	tcpdump-workers@...ts.tcpdump.org,
	Francesco Ruggeri <fruggeri@...stanetworks.com>
Subject: Re: [tcpdump-workers] vlan tagged packets and libpcap breakage

On Tue, 2012-12-11 at 14:36 -0800, Ani Sinha wrote:
> >
> > It is possible to test for the presence of support of the new vlan bpf
> > extensions by attempting to load a filter that uses them.  As only valid
> > filters can be loaded, old kernels that do not support filtering of vlan
> > tags will fail to load the a test filter with uses them.
> 
> Unfortunately I do not see this. The sk_chk_filter() does not have a
> default in the case statement and the check will not detect an unknown
> instruction. It will fail when the filter is run and as far as I can see,
> the packet will be dropped. Something like this might help?
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index c23543c..96338aa 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -548,6 +548,8 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen)
>  			return -EINVAL;
>  		/* Some instructions need special checks */
>  		switch (code) {
> +		/* for unknown instruction, return EINVAL */
> +		default : return -EINVAL;
>  		case BPF_S_ALU_DIV_K:
>  			/* check for division by zero */
>  			if (ftest->k == 0)

This patch is wrong.

Check lines 546, 547, 548 where we do the check for unknown instructions

code = codes[code];
if (!code)
	return -EINVAL;

If you want to test ANCILLARY possible values, its already too late, as
old kernels wont use any patch anyway.



--
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

Powered by blists - more mailing lists