linux-kernel - [tip: core/core] arm64/elf: Disable automatic READ_IMPLIES

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Date:   Mon, 20 Apr 2020 20:03:02 -0000
From:   "tip-bot2 for Kees Cook" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Hector Marco-Gisbert" <hecmargi@....es>,
        Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...e.de>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Catalin Marinas <catalin.marinas@....com>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: core/core] arm64/elf: Disable automatic READ_IMPLIES_EXEC for
 64-bit address spaces

The following commit has been merged into the core/core branch of tip:

Commit-ID:     6e0d6ac5f3d9d90271899f6d340872360fe1caee
Gitweb:        https://git.kernel.org/tip/6e0d6ac5f3d9d90271899f6d340872360fe1caee
Author:        Kees Cook <keescook@...omium.org>
AuthorDate:    Thu, 26 Mar 2020 23:48:20 -07:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Mon, 20 Apr 2020 19:44:27 +02:00

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@....es>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Jason Gunthorpe <jgg@...lanox.com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Link: https://lkml.kernel.org/r/20200327064820.12602-7-keescook@chromium.org
---
 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 0074e9f..0e7df6f 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 aaad4ca..3068d57 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