Re: [PATCH v2 04/15] x86, kaslr: get kaslr_enabled back correctly

Borislav Petkov
2015-03-04T10:18:10Z

On Wed, Mar 04, 2015 at 12:00:37AM -0800, Yinghai Lu wrote:
> commit f47233c2d34f ("x86/mm/ASLR: Propagate base load address calculation")
> is using address as value for kaslr_enabled.
>
> That will random kaslr_enabled get that set or cleared.
> Will have problem for system really have kaslr enabled.
>
> -v2: update changelog.

This is still not good enough. Please do this:

In commit f47233c2d34f we did A. The problem with that is B. Change the
code to do C.

Now you only have to fill out the A,B and C variables with the
respective text which is understandable even for people who don't know
this code.

>
> Fixes: f47233c2d34f ("x86/mm/ASLR: Propagate base load address calculation")
> Cc: Matt Fleming <matt.fleming@intel.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Jiri Kosina <jkosina@suse.cz>
> Acked-by: Jiri Kosina <jkosina@suse.cz>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> ---
> arch/x86/kernel/setup.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 98dc931..05d444f 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -429,7 +429,13 @@ static void __init reserve_initrd(void)
>
> static void __init parse_kaslr_setup(u64 pa_data, u32 data_len)
> {
> - kaslr_enabled = (bool)(pa_data + sizeof(struct setup_data));
> + /* kaslr_setup_data is defined in aslr.c */
> + unsigned char *data;
> + unsigned long offset = sizeof(struct setup_data);
> +
> + data = early_memremap(pa_data, offset + 1);

early_memremap() needs its retval checked before accessing it.

> + kaslr_enabled = *(data + offset);
> + early_memunmap(data, offset + 1);
> }
>
> static void __init parse_setup_data(void)
> --
> 1.8.4.5
>

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
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