netdev - Re: [bpf PATCH 8/9] bpf: sockmap/tls, tls_push_record can not handle zero length skmsg

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Message-ID: <5e1906c73a2b7_20f32b2a8c44e5bc2d@john-XPS-13-9370.notmuch>
Date:   Fri, 10 Jan 2020 15:20:39 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     John Fastabend <john.fastabend@...il.com>,
        Song Liu <song@...nel.org>,
        John Fastabend <john.fastabend@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [bpf PATCH 8/9] bpf: sockmap/tls, tls_push_record can not handle
 zero length skmsg

John Fastabend wrote:
> Song Liu wrote:
> > On Wed, Jan 8, 2020 at 1:17 PM John Fastabend <john.fastabend@...il.com> wrote:
> > >
> > > When passed a zero length skmsg tls_push_record() causes a NULL ptr
> > > deref. To resolve for fixes do a simple length check at start of
> > > routine.
> > 
> > Could you please include the stack dump for the NULL deref?
> > 
> > Thanks,
> > Song
> 
> Sure I'll send a v2 with the stack dump.

Hi Song, I'm having a bit of trouble reproducing this now. I'm going to
drop this patch from the series for now and see if something changed in
crypto layers or elsewhere. I originally saw this on a bit older kernel
so something might changed. Feels a bit like a work-around anyways so
I'll dig into it a bit more.

Either way I'll try and understand this a bit better. Thanks for the
question.