linux-hardening - Re: [PATCH 2/3] usercopy: Cast pointer to an integer once

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Message-ID: <YqcInB4IHXEM7jpC@pc638.lan>
Date:   Mon, 13 Jun 2022 11:51:24 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     Kees Cook <keescook@...omium.org>, linux-mm@...ck.org,
        Uladzislau Rezki <urezki@...il.com>,
        Zorro Lang <zlang@...hat.com>, linux-xfs@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 2/3] usercopy: Cast pointer to an integer once

On Sun, Jun 12, 2022 at 10:32:26PM +0100, Matthew Wilcox (Oracle) wrote:
> Get rid of a lot of annoying casts by setting 'addr' once at the top
> of the function.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  mm/usercopy.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/usercopy.c b/mm/usercopy.c
> index fdd1bed3b90a..31deee7dd2f5 100644
> --- a/mm/usercopy.c
> +++ b/mm/usercopy.c
> @@ -161,19 +161,20 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n,
>  static inline void check_heap_object(const void *ptr, unsigned long n,
>  				     bool to_user)
>  {
> +	uintptr_t addr = (uintptr_t)ptr;
>  	struct folio *folio;
>  
>  	if (is_kmap_addr(ptr)) {
> -		unsigned long page_end = (unsigned long)ptr | (PAGE_SIZE - 1);
> +		unsigned long page_end = addr | (PAGE_SIZE - 1);
>  
> -		if ((unsigned long)ptr + n - 1 > page_end)
> +		if (addr + n - 1 > page_end)
>  			usercopy_abort("kmap", NULL, to_user,
>  					offset_in_page(ptr), n);
>  		return;
>  	}
>  
>  	if (is_vmalloc_addr(ptr)) {
> -		struct vmap_area *area = find_vmap_area((unsigned long)ptr);
> +		struct vmap_area *area = find_vmap_area(addr);
>  		unsigned long offset;
>  
>  		if (!area) {
> @@ -183,8 +184,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
>  
>  		/* XXX: We should also abort for free vmap_areas */
>  
> -		offset = (unsigned long)ptr - area->va_start;
> -		if ((unsigned long)ptr + n > area->va_end)
> +		offset = addr - area->va_start;
> +		if (addr + n > area->va_end)
>  			usercopy_abort("vmalloc", NULL, to_user, offset, n);
>  		return;
>  	}
> -- 
> 2.35.1
> 
Looks good to me: Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>

--
Uladzislau Rezki