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Subject[PATCH v5 6/6] arm64, elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces
Date
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: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/include/asm/elf.h | 4 ++--
fs/compat_binfmt_elf.c | 5 +++++
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 0074e9fd6431..0e7df6f1eb7a 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -105,7 +105,7 @@
*              CPU*: | arm32    | arm64 |
* ELF:              |            |            |
* ---------------------|------------|------------|
- * missing PT_GNU_STACK | exec-all   | exec-all   |
+ * missing PT_GNU_STACK | exec-all   | exec-none  |
* PT_GNU_STACK == RWX  | exec-stack | exec-stack |
* PT_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
--
2.20.1
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