linux-kernel - Re: [PATCH v4 2/4] x86/boot/KASLR: Switch to pass struct mem_vector to process_e820

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Date:   Sun, 9 Jul 2017 07:02:05 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Baoquan He <bhe@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, izumi.taku@...fujitsu.com,
        fanc.fnst@...fujitsu.com, Thomas Garnier <thgarnie@...gle.com>
Subject: Re: [PATCH v4 2/4] x86/boot/KASLR: Switch to pass struct mem_vector
 to process_e820_entry()

On Sun, Jul 9, 2017 at 5:37 AM, Baoquan He <bhe@...hat.com> wrote:
> This makes process_e820_entry() be able to process any kind of memory
> region.
>
> Signed-off-by: Baoquan He <bhe@...hat.com>

Acked-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  arch/x86/boot/compressed/kaslr.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 1485f48aeda1..36ff9f729c43 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -479,31 +479,31 @@ static unsigned long slots_fetch_random(void)
>         return 0;
>  }
>
> -static void process_e820_entry(struct boot_e820_entry *entry,
> +static void process_e820_entry(struct mem_vector *entry,
>                                unsigned long minimum,
>                                unsigned long image_size)
>  {
>         struct mem_vector region, overlap;
>         struct slot_area slot_area;
>         unsigned long start_orig, end;
> -       struct boot_e820_entry cur_entry;
> +       struct mem_vector cur_entry;
>
>         /* On 32-bit, ignore entries entirely above our maximum. */
> -       if (IS_ENABLED(CONFIG_X86_32) && entry->addr >= KERNEL_IMAGE_SIZE)
> +       if (IS_ENABLED(CONFIG_X86_32) && entry->start >= KERNEL_IMAGE_SIZE)
>                 return;
>
>         /* Ignore entries entirely below our minimum. */
> -       if (entry->addr + entry->size < minimum)
> +       if (entry->start + entry->size < minimum)
>                 return;
>
>         /* Ignore entries above memory limit */
> -       end = min(entry->size + entry->addr, mem_limit);
> -       if (entry->addr >= end)
> +       end = min(entry->size + entry->start, mem_limit);
> +       if (entry->start >= end)
>                 return;
> -       cur_entry.addr = entry->addr;
> -       cur_entry.size = end - entry->addr;
> +       cur_entry.start = entry->start;
> +       cur_entry.size = end - entry->start;
>
> -       region.start = cur_entry.addr;
> +       region.start = cur_entry.start;
>         region.size = cur_entry.size;
>
>         /* Give up if slot area array is full. */
> @@ -518,7 +518,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
>                 region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
>
>                 /* Did we raise the address above this e820 region? */
> -               if (region.start > cur_entry.addr + cur_entry.size)
> +               if (region.start > cur_entry.start + cur_entry.size)
>                         return;
>
>                 /* Reduce size by any delta from the original address. */
> @@ -562,6 +562,7 @@ static void process_e820_entries(unsigned long minimum,
>                                  unsigned long image_size)
>  {
>         int i;
> +       struct mem_vector region;
>         struct boot_e820_entry *entry;
>
>         /* Verify potential e820 positions, appending to slots list. */
> @@ -570,7 +571,9 @@ static void process_e820_entries(unsigned long minimum,
>                 /* Skip non-RAM entries. */
>                 if (entry->type != E820_TYPE_RAM)
>                         continue;
> -               process_e820_entry(entry, minimum, image_size);
> +               region.start = entry->addr;
> +               region.size = entry->size;
> +               process_e820_entry(&region, minimum, image_size);
>                 if (slot_area_index == MAX_SLOT_AREA) {
>                         debug_putstr("Aborted e820 scan (slot_areas full)!\n");
>                         break;
> --
> 2.5.5
>



-- 
Kees Cook
Pixel Security