[v3,6/7] arm64, elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces
diff mbox series

Message ID 20200210193049.64362-7-keescook@chromium.org
State New
Headers show
Series
  • binfmt_elf: Update READ_IMPLIES_EXEC logic for modern CPUs
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Commit Message

Kees Cook Feb. 10, 2020, 7:30 p.m. UTC
With arm64 64-bit environments, there should never be a need for automatic
READ_IMPLIES_EXEC, as the architecture has always been execute-bit aware
(as in, the default memory protection should be NX unless a region
explicitly requests to be executable).

Suggested-by: Hector Marco-Gisbert <hecmargi@upv.es>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/include/asm/elf.h | 4 ++--
 fs/compat_binfmt_elf.c       | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

Comments

Catalin Marinas Feb. 12, 2020, 9:28 a.m. UTC | #1
On Mon, Feb 10, 2020 at 11:30:48AM -0800, Kees Cook wrote:
> With arm64 64-bit environments, there should never be a need for automatic
> READ_IMPLIES_EXEC, as the architecture has always been execute-bit aware
> (as in, the default memory protection should be NX unless a region
> explicitly requests to be executable).
> 
> Suggested-by: Hector Marco-Gisbert <hecmargi@upv.es>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Patch
diff mbox series

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 03ada29984a7..ea9221ed68a1 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -105,7 +105,7 @@ 
  *             CPU*: | arm32      | arm64      |
  * ELF:              |            |            |
  * -------------------------------|------------|
- * missing GNU_STACK | exec-all   | exec-all   |
+ * missing GNU_STACK | exec-all   | exec-none  |
  * GNU_STACK == RWX  | exec-stack | exec-stack |
  * GNU_STACK == RW   | exec-none  | exec-none  |
  *
@@ -117,7 +117,7 @@ 
  *  *all arm64 CPUs support NX, so there is no "lacks NX" column.
  *
  */
-#define elf_read_implies_exec(ex,stk)	(stk == EXSTACK_DEFAULT)
+#define compat_elf_read_implies_exec(ex, stk)	(stk == EXSTACK_DEFAULT)
 
 #define CORE_DUMP_USE_REGSET
 #define ELF_EXEC_PAGESIZE	PAGE_SIZE
diff --git a/fs/compat_binfmt_elf.c b/fs/compat_binfmt_elf.c
index aaad4ca1217e..3068d57436b3 100644
--- a/fs/compat_binfmt_elf.c
+++ b/fs/compat_binfmt_elf.c
@@ -113,6 +113,11 @@ 
 #define	arch_setup_additional_pages compat_arch_setup_additional_pages
 #endif
 
+#ifdef	compat_elf_read_implies_exec
+#undef	elf_read_implies_exec
+#define	elf_read_implies_exec compat_elf_read_implies_exec
+#endif
+
 /*
  * Rename a few of the symbols that binfmt_elf.c will define.
  * These are all local so the names don't really matter, but it