linux-kernel - [PATCH 3.16.y-ckt 089/254] x86: Reject x32 executables if x32 ABI not supported

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Date:	Tue, 25 Nov 2014 10:37:19 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Ben Hutchings <ben@...adent.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 089/254] x86: Reject x32 executables if x32 ABI not supported

3.16.7-ckt2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@...adent.org.uk>

commit 0e6d3112a4e95d55cf6dca88f298d5f4b8f29bd1 upstream.

It is currently possible to execve() an x32 executable on an x86_64
kernel that has only ia32 compat enabled.  However all its syscalls
will fail, even _exit().  This usually causes it to segfault.

Change the ELF compat architecture check so that x32 executables are
rejected if we don't support the x32 ABI.

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Link: http://lkml.kernel.org/r/1410120305.6822.9.camel@decadent.org.uk
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 arch/x86/include/asm/elf.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 1a055c81d864..ca3347a9dab5 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -160,8 +160,9 @@ do {						\
 #define elf_check_arch(x)			\
 	((x)->e_machine == EM_X86_64)
 
-#define compat_elf_check_arch(x)		\
-	(elf_check_arch_ia32(x) || (x)->e_machine == EM_X86_64)
+#define compat_elf_check_arch(x)					\
+	(elf_check_arch_ia32(x) ||					\
+	 (IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine == EM_X86_64))
 
 #if __USER32_DS != __USER_DS
 # error "The following code assumes __USER32_DS == __USER_DS"
-- 
2.1.0

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