arm64/elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces

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>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lkml.kernel.org/r/20200327064820.12602-7-keescook@chromium.org

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 0074e9f..0e7df6f 100644 (file)
--- 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 aaad4ca..3068d57 100644 (file)
--- 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