72 lines
3.0 KiB
Diff
72 lines
3.0 KiB
Diff
From: Kees Cook <keescook@chromium.org>
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Date: Mon, 07 Aug 2017 20:15:42 +0000
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Subject: mm: Revert x86_64 and arm64 ELF_ET_DYN_BASE base
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Origin: https://marc.info/?l=linux-arm-kernel&m=150213698426008&w=2
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Bug-Debian: https://bugs.debian.org/869090
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Moving the x86_64 and arm64 PIE base from 0x555555554000 to 0x000100000000
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broke AddressSanitizer. This is a partial revert of:
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commit eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE")
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commit 02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB")
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The AddressSanitizer tool has hard-coded expectations about where
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executable mappings are loaded. The motivation for changing the PIE
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base in the above commits was to avoid the Stack-Clash CVEs that
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allowed executable mappings to get too close to heap and stack. This
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was mainly a problem on 32-bit, but the 64-bit bases were moved too,
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in an effort to proactively protect those systems (proofs of concept
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do exist that show 64-bit collisions, but other recent changes to fix
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stack accounting and setuid behaviors will minimize the impact).
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The new 32-bit PIE base is fine for ASan (since it matches the ET_EXEC
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base), so only the 64-bit PIE base needs to be reverted to let x86 and
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arm64 ASan binaries run again. Future changes to the 64-bit PIE base on
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these architectures can be made optional once a more dynamic method for
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dealing with AddressSanitizer is found. (e.g. always loading PIE into
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the mmap region for marked binaries.)
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Reported-by: Kostya Serebryany <kcc@google.com>
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Cc: stable@vger.kernel.org
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Signed-off-by: Kees Cook <keescook@chromium.org>
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---
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arch/arm64/include/asm/elf.h | 4 ++--
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arch/x86/include/asm/elf.h | 4 ++--
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2 files changed, 4 insertions(+), 4 deletions(-)
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diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
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index acae781f7359..3288c2b36731 100644
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--- a/arch/arm64/include/asm/elf.h
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+++ b/arch/arm64/include/asm/elf.h
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@@ -114,10 +114,10 @@
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/*
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* This is the base location for PIE (ET_DYN with INTERP) loads. On
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- * 64-bit, this is raised to 4GB to leave the entire 32-bit address
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+ * 64-bit, this is above 4GB to leave the entire 32-bit address
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* space open for things that want to use the area for 32-bit pointers.
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*/
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-#define ELF_ET_DYN_BASE 0x100000000UL
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+#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3)
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#ifndef __ASSEMBLY__
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diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
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index 1c18d83d3f09..9aeb91935ce0 100644
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--- a/arch/x86/include/asm/elf.h
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+++ b/arch/x86/include/asm/elf.h
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@@ -247,11 +247,11 @@ extern int force_personality32;
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/*
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* This is the base location for PIE (ET_DYN with INTERP) loads. On
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- * 64-bit, this is raised to 4GB to leave the entire 32-bit address
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+ * 64-bit, this is above 4GB to leave the entire 32-bit address
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* space open for things that want to use the area for 32-bit pointers.
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*/
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#define ELF_ET_DYN_BASE (mmap_is_ia32() ? 0x000400000UL : \
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- 0x100000000UL)
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+ (TASK_SIZE / 3 * 2))
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/* This yields a mask that user programs can use to figure out what
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instruction set this CPU supports. This could be done in user space,
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