[PATCH v3 3/7] x86/elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces
From: Kees Cook <hidden>
Date: 2020-02-10 19:31:08
Also in:
linux-kselftest, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
With modern x86 64-bit environments, there should never be a need for automatic READ_IMPLIES_EXEC, as the architecture is intended to always be execute-bit aware (as in, the default memory protection should be NX unless a region explicitly requests to be executable). There were very old x86_64 systems that lacked the NX bit, but for those, the NX bit is, obviously, unenforceable, so these changes should have no impact on them. Suggested-by: Hector Marco-Gisbert <redacted> Signed-off-by: Kees Cook <redacted> --- arch/x86/include/asm/elf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index a7035065377c..c9b7be0bcad3 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h@@ -287,7 +287,7 @@ extern u32 elf_hwcap2; * CPU: | lacks NX* | has NX, ia32 | has NX, x86_64 | * ELF: | | | | * -------------------------------|------------------|----------------| - * missing GNU_STACK | exec-all | exec-all | exec-all | + * missing GNU_STACK | exec-all | exec-all | exec-none | * GNU_STACK == RWX | exec-stack | exec-stack | exec-stack | * GNU_STACK == RW | exec-none | exec-none | exec-none | *
@@ -303,7 +303,7 @@ extern u32 elf_hwcap2; * */ #define elf_read_implies_exec(ex, executable_stack) \ - (executable_stack == EXSTACK_DEFAULT) + (mmap_is_ia32() && executable_stack == EXSTACK_DEFAULT) struct task_struct;
--
2.20.1
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