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Message-Id: <20200225051307.6401-4-keescook@chromium.org> Date: Mon, 24 Feb 2020 21:13:04 -0800 From: Kees Cook <keescook@...omium.org> To: Borislav Petkov <bp@...en8.de> Cc: Kees Cook <keescook@...omium.org>, Hector Marco-Gisbert <hecmargi@....es>, Jason Gunthorpe <jgg@...lanox.com>, Jason Gunthorpe <jgg@...pe.ca>, Catalin Marinas <catalin.marinas@....com>, Russell King <linux@...linux.org.uk>, Will Deacon <will@...nel.org>, Jann Horn <jannh@...gle.com>, x86@...nel.org, linux-arm-kernel@...ts.infradead.org, kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org Subject: [PATCH v4 3/6] x86/elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces 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 <hecmargi@....es> Signed-off-by: Kees Cook <keescook@...omium.org> Reviewed-by: Jason Gunthorpe <jgg@...lanox.com> --- 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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