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Subject: Re: [PATCH v3] powerpc: Do not make the entire heap executable
To: Kees Cook <keescook@chromium.org>
References: <20160809190822.28856-1-dvlasenk@redhat.com>
 <CAGXu5j+arjRNmGVPeevMBsO6Mdpmw8Lq0GPvJvXNPJeQ8uCWkA@mail.gmail.com>
Cc: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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        Michael Ellerman <mpe@ellerman.id.au>,
        Florian Weimer <fweimer@redhat.com>, Linux-MM <linux-mm@kvack.org>,
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From: Denys Vlasenko <dvlasenk@redhat.com>
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Date: Wed, 10 Aug 2016 14:56:53 +0200
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On 08/10/2016 12:43 AM, Kees Cook wrote:
>> -static int do_brk(unsigned long addr, unsigned long len)
>> +static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long flags)
>>  {
>>         struct mm_struct *mm = current->mm;
>>         struct vm_area_struct *vma, *prev;
>> -       unsigned long flags;
>>         struct rb_node **rb_link, *rb_parent;
>>         pgoff_t pgoff = addr >> PAGE_SHIFT;
>>         int error;
>> @@ -2666,7 +2665,7 @@ static int do_brk(unsigned long addr, unsigned long len)
>>         if (!len)
>>                 return 0;
>>
>> -       flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
>> +       flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
>
> For sanity's sake, should a mask be applied here? i.e. to be extra
> careful about what flags can get passed in?

Maybe... I am leaving it to mm experts.

> Otherwise, this looks okay to me:
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
>
> -Kees