linux-kernel - Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in fill_thread_core

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Message-ID: <20200421034249.GB23230@ZenIV.linux.org.uk>
Date:   Tue, 21 Apr 2020 04:42:49 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, glider@...gle.com,
        adobriyan@...il.com, linux-kernel@...r.kernel.org,
        sunhaoyl@...look.com
Subject: Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in
 fill_thread_core_info()

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@...gle.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.