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From:   Alexander Potapenko <glider@google.com>
Date:   Tue, 21 Apr 2020 10:00:58 +0200
Message-ID: <CAG_fn=VSxh1yXa7yCGHwsxvGT3+DGmJkrqDrMcHGPHBCWRrBMA@mail.gmail.com>
Subject: Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in fill_thread_core_info()
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Alexey Dobriyan <adobriyan@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, sunhaoyl@outlook.com,
        Kees Cook <keescook@chromium.org>
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On Tue, Apr 21, 2020 at 12:33 AM Andrew Morton
<akpm@linux-foundation.org> 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 t=
o
> > the core file and then read by a non-privileged user.
> >
> > ...
> >
> > --- a/fs/binfmt_elf.c
> > +++ b/fs/binfmt_elf.c
> > @@ -1733,7 +1733,7 @@ static int fill_thread_core_info(struct elf_threa=
d_core_info *t,
> >                   (!regset->active || regset->active(t->task, regset) >=
 0)) {
> >                       int ret;
> >                       size_t size =3D regset_size(t->task, regset);
> > -                     void *data =3D kmalloc(size, GFP_KERNEL);
> > +                     void *data =3D kzalloc(size, GFP_KERNEL);
> >                       if (unlikely(!data))
> >                               return 0;
> >                       ret =3D regset->get(t->task, regset,
>
> This seems to be a quite easy way of exposing quite a large amount of
> kernel memory contents, so I think I'll add a cc:stable to this patch?

Correct. Sorry, I forgot about this.

The reporter is also happy with the Reported-by: tag, so you can
ignore the note.

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Alexander Potapenko
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