From: Borislav Petkov <bp@suse.de> To: Thomas Garnier <thgarnie@google.com> Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, Joerg Roedel <jroedel@suse.de>, Dave Young <dyoung@redhat.com>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Lv Zheng <lv.zheng@intel.com>, Baoquan He <bhe@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>, Mark Salter <msalter@redhat.com>, Aleksey Makarov <aleksey.makarov@linaro.org>, Kees Cook <keescook@chromium.org>, Andrew Morton <akpm@linux-foundation.org>, Christian Borntraeger <borntraeger@de.ibm.com>, Fabian Frederick <fabf@skynet.be>, Toshi Kani <toshi.kani@hp.com>, Dan Williams <dan.j.williams@intel.com>, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: Re: [PATCH v1 2/2] x86/KASLR: Increase BRK pages for KASLR memory randomization Date: Tue, 9 Aug 2016 06:01:42 +0200 [thread overview] Message-ID: <20160809040142.GA11449@nazgul.tnic> (raw) In-Reply-To: <1470681607-36883-2-git-send-email-thgarnie@google.com> On Mon, Aug 08, 2016 at 11:40:07AM -0700, Thomas Garnier wrote: > Default implementation expects 6 pages maximum are needed for low page > allocations. If KASLR memory randomization is enabled, the worse case > of e820 layout would require 12 pages (no large pages). It is due to the > PUD level randomization and the variable e820 memory layout. Can't this number of required pages be computed based on the randomization offset or somesuch instead of maxing it out by default on every machine which enables CONFIG_RANDOMIZE_MEMORY? > This bug was found while doing extensive testing of KASLR memory > randomization on different type of hardware. > > Signed-off-by: Thomas Garnier <thgarnie@google.com> > --- > Based on next-20160805 > --- > arch/x86/mm/init.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > index 6209289..3a27e6a 100644 > --- a/arch/x86/mm/init.c > +++ b/arch/x86/mm/init.c > @@ -130,6 +130,14 @@ void __init early_alloc_pgt_buf(void) > unsigned long tables = INIT_PGT_BUF_SIZE; > phys_addr_t base; > > + /* > + * Depending on the machine e860 memory layout and the PUD alignement. e820 alignment > + * We may need twice more pages when KASLR memoy randomization is memory > + * enabled. > + */ > + if (IS_ENABLED(CONFIG_RANDOMIZE_MEMORY)) > + tables *= 2; > + > base = __pa(extend_brk(tables, PAGE_SIZE)); > > pgt_buf_start = base >> PAGE_SHIFT; > -- > 2.8.0.rc3.226.g39d4020 > -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
WARNING: multiple messages have this Message-ID (diff)
From: Borislav Petkov <bp@suse.de> To: Thomas Garnier <thgarnie@google.com> Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, Joerg Roedel <jroedel@suse.de>, Dave Young <dyoung@redhat.com>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Lv Zheng <lv.zheng@intel.com>, Baoquan He <bhe@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>, Mark Salter <msalter@redhat.com>, Aleksey Makarov <aleksey.makarov@linaro.org>, Kees Cook <keescook@chromium.org>, Andrew Morton <akpm@linux-foundation.org>, Christian Borntraeger <borntraeger@de.ibm.com>, Fabian Frederick <fabf@skynet.be>, Toshi Kani <toshi.kani@hp.com>, Dan Williams <dan.j.williams@intel.com>, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [kernel-hardening] Re: [PATCH v1 2/2] x86/KASLR: Increase BRK pages for KASLR memory randomization Date: Tue, 9 Aug 2016 06:01:42 +0200 [thread overview] Message-ID: <20160809040142.GA11449@nazgul.tnic> (raw) In-Reply-To: <1470681607-36883-2-git-send-email-thgarnie@google.com> On Mon, Aug 08, 2016 at 11:40:07AM -0700, Thomas Garnier wrote: > Default implementation expects 6 pages maximum are needed for low page > allocations. If KASLR memory randomization is enabled, the worse case > of e820 layout would require 12 pages (no large pages). It is due to the > PUD level randomization and the variable e820 memory layout. Can't this number of required pages be computed based on the randomization offset or somesuch instead of maxing it out by default on every machine which enables CONFIG_RANDOMIZE_MEMORY? > This bug was found while doing extensive testing of KASLR memory > randomization on different type of hardware. > > Signed-off-by: Thomas Garnier <thgarnie@google.com> > --- > Based on next-20160805 > --- > arch/x86/mm/init.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > index 6209289..3a27e6a 100644 > --- a/arch/x86/mm/init.c > +++ b/arch/x86/mm/init.c > @@ -130,6 +130,14 @@ void __init early_alloc_pgt_buf(void) > unsigned long tables = INIT_PGT_BUF_SIZE; > phys_addr_t base; > > + /* > + * Depending on the machine e860 memory layout and the PUD alignement. e820 alignment > + * We may need twice more pages when KASLR memoy randomization is memory > + * enabled. > + */ > + if (IS_ENABLED(CONFIG_RANDOMIZE_MEMORY)) > + tables *= 2; > + > base = __pa(extend_brk(tables, PAGE_SIZE)); > > pgt_buf_start = base >> PAGE_SHIFT; > -- > 2.8.0.rc3.226.g39d4020 > -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
next prev parent reply other threads:[~2016-08-09 4:02 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-08-08 18:40 [PATCH v1 1/2] x86/KASLR: Fix physical memory calculation on KASLR memory randomization Thomas Garnier 2016-08-08 18:40 ` [kernel-hardening] " Thomas Garnier 2016-08-08 18:40 ` [PATCH v1 2/2] x86/KASLR: Increase BRK pages for " Thomas Garnier 2016-08-08 18:40 ` [kernel-hardening] " Thomas Garnier 2016-08-09 4:01 ` Borislav Petkov [this message] 2016-08-09 4:01 ` [kernel-hardening] " Borislav Petkov 2016-08-09 4:14 ` H. Peter Anvin 2016-08-09 4:14 ` [kernel-hardening] " H. Peter Anvin 2016-08-09 5:16 ` Mika Penttilä 2016-08-09 5:16 ` [kernel-hardening] " Mika Penttilä 2016-08-09 14:47 ` Thomas Garnier 2016-08-09 14:47 ` [kernel-hardening] " Thomas Garnier 2016-08-09 15:07 ` [lkp] [x86/KASLR] 20067c4c13: kernel BUG at arch/x86/mm/physaddr.c:26! kernel test robot 2016-08-09 15:07 ` [kernel-hardening] " kernel test robot 2016-08-09 16:00 ` [PATCH v1 1/2] x86/KASLR: Fix physical memory calculation on KASLR memory randomization Thomas Garnier 2016-08-09 16:00 ` [kernel-hardening] " Thomas Garnier 2016-08-09 16:03 ` Joerg Roedel 2016-08-09 16:03 ` [kernel-hardening] " Joerg Roedel 2016-08-09 16:30 ` Thomas Garnier 2016-08-09 16:30 ` [kernel-hardening] " Thomas Garnier
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