linux-kernel - Re: [PATCH] mm: /proc/pid/smaps_rollup: fix no vma's null-deref

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Date:   Tue, 4 Oct 2022 17:05:57 -0400
From:   Seth Jenkins <sethjenkins@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        linux-mm@...ck.org, stable@...r.kernel.org
Subject: Re: [PATCH] mm: /proc/pid/smaps_rollup: fix no vma's null-deref

I concur, mm-stable looks fine to me as well.

Jann and I conversed today and the tentative decision since this isn't
considered a high-priority security bug is to wait for maple tree to
merge into Linus's branch before submitting this patch to stable.

On Tue, Oct 4, 2022 at 2:46 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Mon,  3 Oct 2022 18:45:31 -0400 FirstName LastName <sethjenkins@...gle.com> wrote:
>
> > From: Seth Jenkins <sethjenkins@...gle.com>
> >
> > Commit 258f669e7e88 ("mm: /proc/pid/smaps_rollup: convert to single value
> > seq_file") introduced a null-deref if there are no vma's in the task in
> > show_smaps_rollup.
> >
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -969,7 +969,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
> >               vma = vma->vm_next;
> >       }
> >
> > -     show_vma_header_prefix(m, priv->mm->mmap->vm_start,
> > +     show_vma_header_prefix(m, priv->mm->mmap ? priv->mm->mmap->vm_start : 0,
> >                              last_vma_end, 0, 0, 0, 0);
> >       seq_pad(m, ' ');
> >       seq_puts(m, "[rollup]\n");
>
> The current mm tree is very different here.  In fact the bug might not
> exist any more.  Please take a look at the mm-stable branch at
> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm?
>
> If no fixes are needed in mm-stable then I guess the process is to
> propose this patch to the stable tree maintainers.
>