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Date:   Tue, 4 Apr 2017 14:10:03 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] mm/usercopy: Drop extra is_vmalloc_or_module check

On Tue, Apr 4, 2017 at 2:09 PM, Laura Abbott <labbott@...hat.com> wrote:
> virt_addr_valid was previously insufficient to validate if virt_to_page
> could be called on an address on arm64. This has since been fixed up
> so there is no need for the extra check. Drop it.
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
> I've given this some testing on my machine and haven't seen any problems
> (e.g. random crashes without the check) and the fix has been in for long
> enough now. I'm in no rush to have this merged so I'm okay if this sits in
> a tree somewhere to get more testing.

Awesome, thanks! I'll get it into my usercopy branch for -next.

-Kees

> ---
>  mm/usercopy.c | 11 -----------
>  1 file changed, 11 deletions(-)
>
> diff --git a/mm/usercopy.c b/mm/usercopy.c
> index d155e12563b1..4d23a0e0e232 100644
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -206,17 +206,6 @@ static inline const char *check_heap_object(const void *ptr, unsigned long n,
>  {
>         struct page *page;
>
> -       /*
> -        * Some architectures (arm64) return true for virt_addr_valid() on
> -        * vmalloced addresses. Work around this by checking for vmalloc
> -        * first.
> -        *
> -        * We also need to check for module addresses explicitly since we
> -        * may copy static data from modules to userspace
> -        */
> -       if (is_vmalloc_or_module_addr(ptr))
> -               return NULL;
> -
>         if (!virt_addr_valid(ptr))
>                 return NULL;
>
> --
> 2.12.1
>



-- 
Kees Cook
Pixel Security

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