linux-kernel - Re: [PATCH] x86/KASLR: move aligning of minimal address to choose_random

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Date:   Thu, 4 Jan 2018 16:04:48 +0600
From:   Alexander Kuleshov <kuleshovmail@...il.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Alexander Kuleshov <kuleshovmail@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Kees Cook <keescook@...omium.org>,
        Dave Jiang <dave.jiang@...el.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/KASLR: move aligning of minimal address to
 choose_random_location()

On 01-04-18, Baoquan He wrote:
> On 01/04/18 at 03:54pm, Alexander Kuleshov wrote:
> > we align minimal possible address during randomization to CONFIG_PHYSICAL_ALIGN
> > two times: during getting of random physical address and virtual
> > address (only for x86_64).
> > 
> > Let's move this to choose_random_location() to not duplicate code in
> > find_random_virt_addr() and find_random_phys_addr().
> > 
> > Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
> > ---
> >  arch/x86/boot/compressed/kaslr.c | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 8199a6187251..8c93e399fdfd 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -673,9 +673,6 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
> >  		return 0;
> >  	}
> >  
> > -	/* Make sure minimum is aligned. */
> > -	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
> > -
> >  	if (process_efi_entries(minimum, image_size))
> >  		return slots_fetch_random();
> >  
> > @@ -688,8 +685,6 @@ static unsigned long find_random_virt_addr(unsigned long minimum,
> >  {
> >  	unsigned long slots, random_addr;
> >  
> > -	/* Make sure minimum is aligned. */
> > -	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
> >  	/* Align image_size for easy slot calculations. */
> >  	image_size = ALIGN(image_size, CONFIG_PHYSICAL_ALIGN);
> >  
> > @@ -738,6 +733,9 @@ void choose_random_location(unsigned long input,
> >  	 */
> >  	min_addr = min(*output, 512UL << 20);
> >  
> > +	/* Make sure minimum is aligned. */
> > +	min_addr = ALIGN(min_addr, CONFIG_PHYSICAL_ALIGN);
> 
> Hmm, the min_addr is passed to find_random_phys_addr(), but not to
> find_random_virt_addr().

ah, yes, sorry for noise then