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[tip:x86/urgent] x86/mm/KASLR: Exclude EFI region from KASLR VA space randomization

From tip-bot for Baoquan He <tipbot@zytor.com>
Newsgroups linux.kernel
Subject [tip:x86/urgent] x86/mm/KASLR: Exclude EFI region from KASLR VA space randomization
Date 2017-03-24 09:20 +0100
Message-ID <tosBY-79h-7@gated-at.bofh.it> (permalink)
References <topE5-4WE-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Commit-ID:  a46f60d76004965e5669dbf3fc21ef3bc3632eb4
Gitweb:     http://git.kernel.org/tip/a46f60d76004965e5669dbf3fc21ef3bc3632eb4
Author:     Baoquan He <bhe@redhat.com>
AuthorDate: Fri, 24 Mar 2017 12:59:52 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 24 Mar 2017 09:04:27 +0100

x86/mm/KASLR: Exclude EFI region from KASLR VA space randomization

Currently KASLR is enabled on three regions: the direct mapping of physical
memory, vamlloc and vmemmap. However the EFI region is also mistakenly
included for VA space randomization because of misusing EFI_VA_START macro
and assuming EFI_VA_START < EFI_VA_END.

(This breaks kexec and possibly other things that rely on stable addresses.)

The EFI region is reserved for EFI runtime services virtual mapping which
should not be included in KASLR ranges. In Documentation/x86/x86_64/mm.txt,
we can see:

  ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space

EFI uses the space from -4G to -64G thus EFI_VA_START > EFI_VA_END,
Here EFI_VA_START = -4G, and EFI_VA_END = -64G.

Changing EFI_VA_START to EFI_VA_END in mm/kaslr.c fixes this problem.

Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Bhupesh Sharma <bhsharma@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
Acked-by: Thomas Garnier <thgarnie@google.com>
Cc: <stable@vger.kernel.org> #4.8+
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1490331592-31860-1-git-send-email-bhe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/mm/kaslr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 887e571..aed2064 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -48,7 +48,7 @@ static const unsigned long vaddr_start = __PAGE_OFFSET_BASE;
 #if defined(CONFIG_X86_ESPFIX64)
 static const unsigned long vaddr_end = ESPFIX_BASE_ADDR;
 #elif defined(CONFIG_EFI)
-static const unsigned long vaddr_end = EFI_VA_START;
+static const unsigned long vaddr_end = EFI_VA_END;
 #else
 static const unsigned long vaddr_end = __START_KERNEL_map;
 #endif
@@ -105,7 +105,7 @@ void __init kernel_randomize_memory(void)
 	 */
 	BUILD_BUG_ON(vaddr_start >= vaddr_end);
 	BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) &&
-		     vaddr_end >= EFI_VA_START);
+		     vaddr_end >= EFI_VA_END);
 	BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) ||
 		      IS_ENABLED(CONFIG_EFI)) &&
 		     vaddr_end >= __START_KERNEL_map);

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Thread

[PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into KASLR VA space for randomization Baoquan He <bhe@redhat.com> - 2017-03-24 06:10 +0100
  [tip:x86/urgent] x86/mm/KASLR: Exclude EFI region from KASLR VA  space randomization tip-bot for Baoquan He <tipbot@zytor.com> - 2017-03-24 09:20 +0100
  Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ingo Molnar <mingo@kernel.org> - 2017-03-24 09:20 +0100
    Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Baoquan He <bhe@redhat.com> - 2017-03-24 09:40 +0100
      Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Dave Young <dyoung@redhat.com> - 2017-03-24 09:50 +0100
        Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ingo Molnar <mingo@kernel.org> - 2017-03-24 10:30 +0100
          Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Borislav Petkov <bp@alien8.de> - 2017-03-24 10:40 +0100
          Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-03-24 10:40 +0100
            Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Borislav Petkov <bp@alien8.de> - 2017-03-24 10:50 +0100
              Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-03-24 11:00 +0100
            Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Borislav Petkov <bp@alien8.de> - 2017-03-24 10:50 +0100
              Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-03-24 10:50 +0100
            Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ingo Molnar <mingo@kernel.org> - 2017-03-24 11:40 +0100
              Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-03-24 11:50 +0100
                Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Ingo Molnar <mingo@kernel.org> - 2017-03-24 12:00 +0100
          Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Baoquan He <bhe@redhat.com> - 2017-03-24 13:00 +0100
    Re: [PATCH v2] x86/mm/KASLR: EFI region is mistakenly included into  KASLR VA space for randomization Dave Young <dyoung@redhat.com> - 2017-03-24 10:00 +0100

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