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From: Kees Cook <keescook@chromium.org>
To: Yinghai Lu <yinghai@kernel.org>
Cc: Matt Fleming <matt.fleming@intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@suse.de>, Baoquan He <bhe@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jiri Kosina <jkosina@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>,
	"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>
Subject: Re: [PATCH v3 5/7] x86, kaslr: Consolidate mem_avoid array filling
Date: Mon, 9 Mar 2015 18:00:07 -0700	[thread overview]
Message-ID: <CAGXu5j+exWabf=LdpkBtipcRYDVW=sH4LZf01P3RoSaKK7iYYA@mail.gmail.com> (raw)
In-Reply-To: <1425766041-6551-6-git-send-email-yinghai@kernel.org>

On Sat, Mar 7, 2015 at 2:07 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> Now ZO sit end of the buffer, we can find out where is ZO text
> and data/bss etc.
>
> [input, input+input_size) is copied compressed kernel, not the whole ZO.
> [output, output+init_size) is the buffer for VO.
>
> [input+input_size, output+init_size) is [_text, _end) for ZO.
> that could be first range in mem_avoid. We don't need to guess that anymore.
>
> That area already include heap and stack for ZO running. So we don't need
> to put them into mem_avoid array.
>
> We need to put boot_params into the mem_avoid too. As with 64bit bootloader
> could put it anywhere.

This may be a stupid question, but are boot_params being used outside
of the compressed loader? If so, it might make sense to split that
change into a separate patch to go to stable, if it's causing
problems. (And document what problem is getting solved.)

-Kees

>
> Also change output_size referring to init_size, as we pass init_size instead.
>
> Cc: Kees Cook <keescook@chromium.org>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> ---
>  arch/x86/boot/compressed/aslr.c | 29 ++++++++++++++---------------
>  arch/x86/boot/compressed/misc.h |  4 ++--
>  2 files changed, 16 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
> index 7083c16..a279514 100644
> --- a/arch/x86/boot/compressed/aslr.c
> +++ b/arch/x86/boot/compressed/aslr.c
> @@ -116,7 +116,7 @@ struct mem_vector {
>         unsigned long size;
>  };
>
> -#define MEM_AVOID_MAX 5
> +#define MEM_AVOID_MAX 4
>  static struct mem_vector mem_avoid[MEM_AVOID_MAX];
>
>  static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
> @@ -142,7 +142,7 @@ static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
>  }
>
>  static void mem_avoid_init(unsigned long input, unsigned long input_size,
> -                          unsigned long output, unsigned long output_size)
> +                          unsigned long output, unsigned long init_size)
>  {
>         u64 initrd_start, initrd_size;
>         u64 cmd_line, cmd_line_size;
> @@ -151,10 +151,13 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>
>         /*
>          * Avoid the region that is unsafe to overlap during
> -        * decompression (see calculations at top of misc.c).
> +        * decompression.
> +        * As we already move ZO (arch/x86/boot/compressed/vmlinux)
> +        * to the end of buffer, [input+input_size, output+init_size)
> +        * has [_text, _end) for ZO.
>          */
> -       unsafe_len = (output_size >> 12) + 32768 + 18;
> -       unsafe = (unsigned long)input + input_size - unsafe_len;
> +       unsafe_len = output + init_size - (input + input_size);
> +       unsafe = (unsigned long)input + input_size;
>         mem_avoid[0].start = unsafe;
>         mem_avoid[0].size = unsafe_len;
>
> @@ -176,13 +179,9 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>         mem_avoid[2].start = cmd_line;
>         mem_avoid[2].size = cmd_line_size;
>
> -       /* Avoid heap memory. */
> -       mem_avoid[3].start = (unsigned long)free_mem_ptr;
> -       mem_avoid[3].size = BOOT_HEAP_SIZE;
> -
> -       /* Avoid stack memory. */
> -       mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
> -       mem_avoid[4].size = BOOT_STACK_SIZE;
> +       /* Avoid params */
> +       mem_avoid[3].start = (unsigned long)real_mode;
> +       mem_avoid[3].size = sizeof(*real_mode);
>  }
>
>  /* Does this memory vector overlap a known avoided area? */
> @@ -327,7 +326,7 @@ unsigned char *choose_kernel_location(struct boot_params *params,
>                                       unsigned char *input,
>                                       unsigned long input_size,
>                                       unsigned char *output,
> -                                     unsigned long output_size)
> +                                     unsigned long init_size)
>  {
>         unsigned long choice = (unsigned long)output;
>         unsigned long random;
> @@ -349,10 +348,10 @@ unsigned char *choose_kernel_location(struct boot_params *params,
>
>         /* Record the various known unsafe memory ranges. */
>         mem_avoid_init((unsigned long)input, input_size,
> -                      (unsigned long)output, output_size);
> +                      (unsigned long)output, init_size);
>
>         /* Walk e820 and find a random address. */
> -       random = find_random_addr(choice, output_size);
> +       random = find_random_addr(choice, init_size);
>         if (!random) {
>                 debug_putstr("KASLR could not find suitable E820 region...\n");
>                 goto out;
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index ee3576b..23156e7 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -61,7 +61,7 @@ unsigned char *choose_kernel_location(struct boot_params *params,
>                                       unsigned char *input,
>                                       unsigned long input_size,
>                                       unsigned char *output,
> -                                     unsigned long output_size);
> +                                     unsigned long init_size);
>  /* cpuflags.c */
>  bool has_cpuflag(int flag);
>  #else
> @@ -70,7 +70,7 @@ unsigned char *choose_kernel_location(struct boot_params *params,
>                                       unsigned char *input,
>                                       unsigned long input_size,
>                                       unsigned char *output,
> -                                     unsigned long output_size)
> +                                     unsigned long init_size)
>  {
>         return output;
>  }
> --
> 1.8.4.5
>



-- 
Kees Cook
Chrome OS Security

  reply	other threads:[~2015-03-10  1:00 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-07 22:07 [PATCH v3 0/7] x86, boot: clean up kasl Yinghai Lu
2015-03-07 22:07 ` [PATCH v3 1/7] x86, kaslr: Use init_size instead of run_size Yinghai Lu
2015-03-09 12:49   ` Borislav Petkov
2015-03-09 15:58     ` Ingo Molnar
2015-03-09 15:58       ` Borislav Petkov
2015-03-09 19:35     ` Yinghai Lu
2015-03-09 20:00       ` Borislav Petkov
2015-03-09 20:06         ` Yinghai Lu
2015-03-09 20:18           ` Borislav Petkov
2015-03-09 21:28             ` Yinghai Lu
2015-03-10  0:42   ` Kees Cook
2015-03-13 12:27   ` Ingo Molnar
2015-03-14  2:47     ` Yinghai Lu
2015-03-14  7:53       ` Ingo Molnar
2015-03-14  9:59         ` Borislav Petkov
2015-03-16 10:06           ` [PATCH] Revert "x86/mm/ASLR: Propagate base load address calculation" Borislav Petkov
2015-03-16 12:11             ` [tip:x86/urgent] " tip-bot for Borislav Petkov
2015-03-16 19:32               ` Yinghai Lu
2015-03-16 13:56             ` [PATCH] " Jiri Kosina
2015-03-16 19:15               ` Yinghai Lu
2015-03-17  8:14                 ` Ingo Molnar
2015-03-07 22:07 ` [PATCH v3 2/7] x86, boot: Move ZO to end of buffer Yinghai Lu
2015-03-10  0:54   ` Kees Cook
2015-03-10  1:04     ` Yinghai Lu
2015-03-10  5:59     ` Borislav Petkov
2015-03-10  8:00   ` Borislav Petkov
2015-03-10  9:34     ` Jiri Kosina
2015-03-10  9:35       ` Borislav Petkov
2015-03-10 15:11     ` Yinghai Lu
2015-03-10 15:13       ` Borislav Petkov
2015-03-10 16:59     ` Kees Cook
2015-03-07 22:07 ` [PATCH v3 3/7] x86, boot: Don't overlap VO with ZO data Yinghai Lu
2015-03-10  9:34   ` Borislav Petkov
2015-03-10 15:05     ` Yinghai Lu
2015-03-10 15:10       ` Borislav Petkov
2015-03-10 15:17         ` Yinghai Lu
2015-03-10 15:21           ` Borislav Petkov
2015-03-10 15:42             ` Yinghai Lu
2015-03-10 15:48               ` Borislav Petkov
2015-03-10 19:29                 ` Yinghai Lu
2015-03-07 22:07 ` [PATCH v3 4/7] x86, kaslr: Access the correct kaslr_enabled variable Yinghai Lu
2015-03-10  0:55   ` Kees Cook
2015-03-07 22:07 ` [PATCH v3 5/7] x86, kaslr: Consolidate mem_avoid array filling Yinghai Lu
2015-03-10  1:00   ` Kees Cook [this message]
2015-03-10  1:10     ` Yinghai Lu
2015-03-10  1:26       ` Kees Cook
2015-03-07 22:07 ` [PATCH v3 6/7] x86, boot: Split kernel_ident_mapping_init to another file Yinghai Lu
2015-03-10  1:03   ` Kees Cook
2015-03-07 22:07 ` [PATCH v3 7/7] x86, kaslr, 64bit: Set new or extra ident_mapping Yinghai Lu
2015-03-10  1:09   ` Kees Cook
2015-03-10  1:14     ` Yinghai Lu
2015-03-10  6:54       ` Yinghai Lu
2015-03-10  0:39 ` [PATCH v3 0/7] x86, boot: clean up kasl Kees Cook
2015-03-10  0:54   ` Yinghai Lu

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