From: Kees Cook Date: Fri, 27 Mar 2020 06:48:17 +0000 (-0700) Subject: x86/elf: Disable automatic READ_IMPLIES_EXEC on 64-bit X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9fccc5c0c99f238aa1b0460fccbdb30a887e7036;p=linux.git x86/elf: Disable automatic READ_IMPLIES_EXEC on 64-bit 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 Signed-off-by: Kees Cook Signed-off-by: Borislav Petkov Reviewed-by: Jason Gunthorpe Link: https://lkml.kernel.org/r/20200327064820.12602-4-keescook@chromium.org --- diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 397a1c74433ec..452beed7892bb 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 PT_GNU_STACK | exec-all   | exec-all         | exec-all       | + * missing PT_GNU_STACK | exec-all   | exec-all         | exec-none      | * PT_GNU_STACK == RWX  | exec-stack | exec-stack       | exec-stack     | * PT_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;