[3.13.y.z extended stable] Patch "x86: Reject x32 executables if x32 ABI not supported" has been added to staging queue

[Kamal Mostafa]

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-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.10.

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

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 86e384a4963cb512eb87cdea01788d1321fb096a 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: Kamal Mostafa <kamal 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 9c999c1..01f15b2 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -155,8 +155,9 @@ 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"
--
1.9.1