linux-kernel - Re: [tip:x86/boot] ACPI/NUMA: Add warning message if the padding size for KASLR is not enough

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Date:   Tue, 2 Oct 2018 17:19:43 -0400
From:   Masayoshi Mizuma <msys.mizuma@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     m.mizuma@...fujitsu.com, bhe@...hat.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, hpa@...or.com, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/boot] ACPI/NUMA: Add warning message if the padding
 size for KASLR is not enough

On Tue, Oct 02, 2018 at 05:05:18PM +0200, Borislav Petkov wrote:
> On Tue, Oct 02, 2018 at 03:18:41AM -0700, tip-bot for Masayoshi Mizuma wrote:
> > Commit-ID:  3b054ca88c4f4dd5f516a12d4b6d6bd0ae826f41
> > Gitweb:     https://git.kernel.org/tip/3b054ca88c4f4dd5f516a12d4b6d6bd0ae826f41
> > Author:     Masayoshi Mizuma <m.mizuma@...fujitsu.com>
> > AuthorDate: Mon, 1 Oct 2018 10:08:42 -0400
> > Committer:  Ingo Molnar <mingo@...nel.org>
> > CommitDate: Tue, 2 Oct 2018 11:47:21 +0200
> > 
> > ACPI/NUMA: Add warning message if the padding size for KASLR is not enough
> > 
> > Add warning message if the padding size for KASLR,
> > rand_mem_physical_padding, is not enough. The message also
> > says the suitable padding size.
> > 
> > Signed-off-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
> > Cc: Baoquan He <bhe@...hat.com>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Masayoshi Mizuma <msys.mizuma@...il.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Link: http://lkml.kernel.org/r/20181001140843.26137-3-msys.mizuma@gmail.com
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > ---
> >  arch/x86/include/asm/setup.h |  2 ++
> >  drivers/acpi/numa.c          | 14 ++++++++++++++
> >  2 files changed, 16 insertions(+)
> > 
> > diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
> > index ae13bc974416..65a5bf8f6aba 100644
> > --- a/arch/x86/include/asm/setup.h
> > +++ b/arch/x86/include/asm/setup.h
> > @@ -80,6 +80,8 @@ static inline unsigned long kaslr_offset(void)
> >  	return (unsigned long)&_text - __START_KERNEL;
> >  }
> >  
> > +extern int rand_mem_physical_padding;
> > +
> >  /*
> >   * Do NOT EVER look at the BIOS memory size location.
> >   * It does not work on many machines.
> > diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
> > index 85167603b9c9..3d69834c692f 100644
> > --- a/drivers/acpi/numa.c
> > +++ b/drivers/acpi/numa.c
> > @@ -32,6 +32,7 @@
> >  #include <linux/numa.h>
> >  #include <linux/nodemask.h>
> >  #include <linux/topology.h>
> > +#include <asm/setup.h>
> >  
> >  static nodemask_t nodes_found_map = NODE_MASK_NONE;
> >  
> > @@ -435,6 +436,7 @@ acpi_table_parse_srat(enum acpi_srat_type id,
> >  int __init acpi_numa_init(void)
> >  {
> >  	int cnt = 0;
> > +	u64 max_possible_phys, max_actual_phys, threshold;
> >  
> >  	if (acpi_disabled)
> >  		return -EINVAL;
> > @@ -463,6 +465,18 @@ int __init acpi_numa_init(void)
> >  
> >  		cnt = acpi_table_parse_srat(ACPI_SRAT_TYPE_MEMORY_AFFINITY,
> >  					    acpi_parse_memory_affinity, 0);
> > +
> > +		/* check the padding size for KASLR is enough. */
> > +		if (parsed_numa_memblks && kaslr_enabled()) {
> > +			max_actual_phys = roundup(PFN_PHYS(max_pfn), 1ULL << 40);
> > +			max_possible_phys = roundup(PFN_PHYS(max_possible_pfn), 1ULL << 40);
> > +			threshold = max_actual_phys + ((u64)rand_mem_physical_padding << 40);
> 
> Nope, not really:
> 
> ld: drivers/acpi/numa.o: in function `acpi_numa_init':
> /home/boris/kernel/linux/drivers/acpi/numa.c:473: undefined reference to `rand_mem_physical_padding'
> make: *** [Makefile:1030: vmlinux] Error 1
> 
> due to CONFIG_RANDOMIZE_MEMORY=n in my .config.
> 
> You need to add a fix ontop which adds a function
> get_rand_mem_physical_padding() which is defined in CONFIG_RANDOMIZE_MEMORY=y
> and outside returns 0.
> 
> And then make that rand_mem_physical_padding static and do not export it
> to anything outside of kaslr.c but use the accessor.

Thank you for the report and suggetions!
I'll fix it and resubmit soon.

Thanks,
Masa