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

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Date:   Tue, 12 May 2020 10:20:21 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     Al Viro <viro@...iv.linux.org.uk>
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, May 12, 2020 at 5:44 AM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> On Tue, May 12, 2020 at 02:09:01AM +0100, Al Viro wrote:
> > 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.
>
> Actually, more interesting question would be your /proc/cpuinfo...

See both attached.
I was also able to reproduce the bug on my desktop using the attached
dump.sh script.

-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
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View attachment "cpuinfo.txt" of type "text/plain" (5608 bytes)

View attachment "config.txt" of type "text/plain" (211282 bytes)

Download attachment "dump.sh" of type "application/x-shellscript" (483 bytes)