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Groups > linux.kernel > #1717749

[PATCH 4.12 22/41] mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base changes

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4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@chromium.org>

commit c715b72c1ba406f133217b509044c38d8e714a37 upstream.

Moving the x86_64 and arm64 PIE base from 0x555555554000 to 0x000100000000
broke AddressSanitizer.  This is a partial revert of:

  eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE")
  02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB")

The AddressSanitizer tool has hard-coded expectations about where
executable mappings are loaded.

The motivation for changing the PIE base in the above commits was to
avoid the Stack-Clash CVEs that allowed executable mappings to get too
close to heap and stack.  This was mainly a problem on 32-bit, but the
64-bit bases were moved too, in an effort to proactively protect those
systems (proofs of concept do exist that show 64-bit collisions, but
other recent changes to fix stack accounting and setuid behaviors will
minimize the impact).

The new 32-bit PIE base is fine for ASan (since it matches the ET_EXEC
base), so only the 64-bit PIE base needs to be reverted to let x86 and
arm64 ASan binaries run again.  Future changes to the 64-bit PIE base on
these architectures can be made optional once a more dynamic method for
dealing with AddressSanitizer is found.  (e.g.  always loading PIE into
the mmap region for marked binaries.)

Link: http://lkml.kernel.org/r/20170807201542.GA21271@beast
Fixes: eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE")
Fixes: 02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Kostya Serebryany <kcc@google.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/include/asm/elf.h |    4 ++--
 arch/x86/include/asm/elf.h   |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -114,10 +114,10 @@
 
 /*
  * This is the base location for PIE (ET_DYN with INTERP) loads. On
- * 64-bit, this is raised to 4GB to leave the entire 32-bit address
+ * 64-bit, this is above 4GB to leave the entire 32-bit address
  * space open for things that want to use the area for 32-bit pointers.
  */
-#define ELF_ET_DYN_BASE		0x100000000UL
+#define ELF_ET_DYN_BASE		(2 * TASK_SIZE_64 / 3)
 
 #ifndef __ASSEMBLY__
 
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -247,11 +247,11 @@ extern int force_personality32;
 
 /*
  * This is the base location for PIE (ET_DYN with INTERP) loads. On
- * 64-bit, this is raised to 4GB to leave the entire 32-bit address
+ * 64-bit, this is above 4GB to leave the entire 32-bit address
  * space open for things that want to use the area for 32-bit pointers.
  */
 #define ELF_ET_DYN_BASE		(mmap_is_ia32() ? 0x000400000UL : \
-						  0x100000000UL)
+						  (TASK_SIZE / 3 * 2))
 
 /* This yields a mask that user programs can use to figure out what
    instruction set this CPU supports.  This could be done in user space,

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[PATCH 4.12 00/41] 4.12.9-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 28/41] perf/x86: Fix RDPMC vs. mm_struct tracking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 09/41] md: fix test in md_write_start() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 31/41] x86/elf: Remove the unnecessary ADDR_NO_RANDOMIZE checks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 19/41] mm/cma_debug.c: fix stack corruption due to sprintf usage Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 21/41] mm/vmalloc.c: dont unconditonally use __GFP_HIGHMEM Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 02/41] parisc: pci memory bar assignment fails with 64bit kernels on dino/cujo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 10/41] md: always clear ->safemode when md_check_recovery gets the mddev lock. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 25/41] blk-mq-pci: add a fallback when pci_irq_get_affinity returns NULL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 05/41] drm/i915: Perform an invalidate prior to executing golden renderstate Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 22/41] mm: revert x86_64 and arm64 ELF_ET_DYN_BASE base changes Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 01/41] audit: Fix use after free in audit_remove_watch_rule() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 27/41] xen-blkfront: use a right index when checking requests Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 18/41] mm: fix double mmap_sem unlock on MMF_UNSTABLE enforced SIGBUS Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 32/41] irqchip/atmel-aic: Fix unbalanced of_node_put() in aic_common_irq_fixup() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  [PATCH 4.12 29/41] x86/asm/64: Clear AC on NMI entries Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-22 21:30 +0200
  Re: [PATCH 4.12 00/41] 4.12.9-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-08-23 02:40 +0200
    Re: [PATCH 4.12 00/41] 4.12.9-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-23 02:50 +0200

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