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Date:   Tue, 21 Apr 2020 04:42:49 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Kees Cook <keescook@chromium.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>, glider@google.com,
        adobriyan@gmail.com, linux-kernel@vger.kernel.org,
        sunhaoyl@outlook.com
Subject: Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in
 fill_thread_core_info()
Message-ID: <20200421034249.GB23230@ZenIV.linux.org.uk>
References: <20200419100848.63472-1-glider@google.com>
 <20200420153352.6682533e794f591dae7aafbc@linux-foundation.org>
 <202004201540.01C8F82B@keescook>
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On Mon, Apr 20, 2020 at 03:41:40PM -0700, Kees Cook wrote:
> On Mon, Apr 20, 2020 at 03:33:52PM -0700, Andrew Morton wrote:
> > On Sun, 19 Apr 2020 12:08:48 +0200 glider@google.com wrote:
> > 
> > > KMSAN reported uninitialized data being written to disk when dumping
> > > core. As a result, several kilobytes of kmalloc memory may be written to
> > > the core file and then read by a non-privileged user.
> 
> Ewww. That's been there for 12 years. Did something change in
> regset_size() or regset->get()? Do you know what leaves the hole?

Not lately and I would also like to hear the details; which regset it is?
Should be reasonably easy to find - just memset() the damn thing to something
recognizable, do whatever triggers that KMSAN report and look at that
resulting coredump.