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

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Date:   Tue, 21 Apr 2020 10:00:58 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, sunhaoyl@...look.com,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in fill_thread_core_info()

On Tue, Apr 21, 2020 at 12:33 AM Andrew Morton
<akpm@...ux-foundation.org> 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.
> >
> > ...
> >
> > --- a/fs/binfmt_elf.c
> > +++ b/fs/binfmt_elf.c
> > @@ -1733,7 +1733,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
> >                   (!regset->active || regset->active(t->task, regset) > 0)) {
> >                       int ret;
> >                       size_t size = regset_size(t->task, regset);
> > -                     void *data = kmalloc(size, GFP_KERNEL);
> > +                     void *data = kzalloc(size, GFP_KERNEL);
> >                       if (unlikely(!data))
> >                               return 0;
> >                       ret = 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.

-- 
Alexander Potapenko
Software Engineer

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