netdev - Re: [PATCH] lsm: make security_socket_getpeersec_stream() sockptr

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Date:   Fri, 4 Nov 2022 23:32:05 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     John Johansen <john.johansen@...onical.com>
Cc:     linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        netdev@...r.kernel.org,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [PATCH] lsm: make security_socket_getpeersec_stream() sockptr_t safe

On Mon, Oct 31, 2022 at 5:59 AM John Johansen
<john.johansen@...onical.com> wrote:
> On 10/10/22 14:58, Paul Moore wrote:
> > Commit 4ff09db1b79b ("bpf: net: Change sk_getsockopt() to take the
> > sockptr_t argument") made it possible to call sk_getsockopt()
> > with both user and kernel address space buffers through the use of
> > the sockptr_t type.  Unfortunately at the time of conversion the
> > security_socket_getpeersec_stream() LSM hook was written to only
> > accept userspace buffers, and in a desire to avoid having to change
> > the LSM hook the commit author simply passed the sockptr_t's
> > userspace buffer pointer.  Since the only sk_getsockopt() callers
> > at the time of conversion which used kernel sockptr_t buffers did
> > not allow SO_PEERSEC, and hence the
> > security_socket_getpeersec_stream() hook, this was acceptable but
> > also very fragile as future changes presented the possibility of
> > silently passing kernel space pointers to the LSM hook.
> >
> > There are several ways to protect against this, including careful
> > code review of future commits, but since relying on code review to
> > catch bugs is a recipe for disaster and the upstream eBPF maintainer
> > is "strongly against defensive programming", this patch updates the
> > LSM hook, and all of the implementations to support sockptr_t and
> > safely handle both user and kernel space buffers.
> >
> > Signed-off-by: Paul Moore <paul@...l-moore.com>
>
> looks good to me

Thanks.  I just merged this into lsm/next.

> Acked-by: John Johansen <john.johansen@...onical.com>

-- 
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