[3.16.y-ckt stable] Patch "x86: Reject x32 executables if x32 ABI not supported" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    x86: Reject x32 executables if x32 ABI not supported

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 62c3b5a2a6cdd672b0b657b84b6a7ffd3d8661ac Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben at decadent.org.uk>
Date: Sun, 7 Sep 2014 21:05:05 +0100
Subject: x86: Reject x32 executables if x32 ABI not supported

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 at decadent.org.uk>
Link: http://lkml.kernel.org/r/1410120305.6822.9.camel@decadent.org.uk
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.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