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

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Date:   Tue, 12 May 2020 02:09:01 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, sunhaoyl@...look.com
Subject: Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in
 fill_thread_core_info()

On Tue, Apr 21, 2020 at 10:14:25AM +0200, Alexander Potapenko wrote:
> > 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.
> 
> The bug is easily triggerable by the following program:
> 
> ================================================
> int main() {
>   volatile char *c = 0;
>   (void)*c;
>   return 0;
> }
> ================================================
> 
> in my QEMU after I do `ulimit -c 10000`.

.config, please - I hadn't been able to reproduce that on mine.
Coredump obviously does happen, but not a trace of the poison
is there - with your memset(data, 0xae, size) added, that is.