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Date: Fri, 25 Feb 2011 11:50:33 -0500
From: Steve Grubb <sgrubb@...hat.com>
To: Nelson Elhage <nelhage@...lice.com>
Cc: oss-security@...ts.openwall.com
Subject: Re: CVE request: libcgroup: Failure to verify netlink messages
On Friday, February 25, 2011 10:43:20 am Nelson Elhage wrote:
> On Fri, Feb 25, 2011 at 10:20:02AM -0500, Steve Grubb wrote:
> > The current patch does not check if (from_nla_len != sizeof(from_nla))
> > before making decisions based on the header. I contacted upstream about
> > this.
>
> From my reading of the netlink code, recvmsg() / recvfrom() on a netlink
> socket will never return a from_nla_len != sizeof(struct sockaddaddr_nl).
> Am I missing something, did this change at some point, or are you just
> suggesting general paranoid good practice? It's probably good advice in
> any case, I'm just curious whether you're aware of cases where this can
> actually be a problem.
I don't know what is considered the ultimate authority on this. You can look at libnl
in lib/nl.c you find this:
466 if (msg.msg_namelen != sizeof(struct sockaddr_nl)) {
467 free(msg.msg_control);
468 free(*buf);
469 return -NLE_NOADDR;
470 }
There are many projects that do something similar. However, looking at glibc, they do
other kinds of validation like the sequence number.
-Steve
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