[3.13.y-ckt stable] Patch "x86/entry/compat: Add missing CLAC to entry_INT80_32" has been added to the 3.13.y-ckt tree

[Kamal Mostafa]

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

    x86/entry/compat: Add missing CLAC to entry_INT80_32

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

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt36.

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-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From d618e00c0f297f9206841e0d1d45c5e142fef974 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto at kernel.org>
Date: Wed, 24 Feb 2016 12:18:49 -0800
Subject: x86/entry/compat: Add missing CLAC to entry_INT80_32

commit 3d44d51bd339766f0178f0cf2e8d048b4a4872aa upstream.

This doesn't seem to fix a regression -- I don't think the CLAC was
ever there.

I double-checked in a debugger: entries through the int80 gate do
not automatically clear AC.

Stable maintainers: I can provide a backport to 4.3 and earlier if
needed.  This needs to be backported all the way to 3.10.

Reported-by: Brian Gerst <brgerst at gmail.com>
Signed-off-by: Andy Lutomirski <luto at kernel.org>
Cc: Andy Lutomirski <luto at amacapital.net>
Cc: Borislav Petkov <bp at alien8.de>
Cc: Denys Vlasenko <dvlasenk at redhat.com>
Cc: H. Peter Anvin <hpa at zytor.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Fixes: 63bcff2a307b ("x86, smap: Add STAC and CLAC instructions to control user space access")
Link: http://lkml.kernel.org/r/b02b7e71ae54074be01fc171cbd4b72517055c0e.1456345086.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo at kernel.org>
[ kamal: backport to 3.10 through 3.19-stable: file rename; context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/ia32/ia32entry.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 92a2e93..b74ac9c 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -422,6 +422,7 @@ ENTRY(ia32_syscall)
 	/*CFI_REL_OFFSET	cs,CS-RIP*/
 	CFI_REL_OFFSET	rip,RIP-RIP
 	PARAVIRT_ADJUST_EXCEPTION_FRAME
+	ASM_CLAC			/* Do this early to minimize exposure */
 	SWAPGS
 	/*
 	 * No need to follow this irqs on/off section: the syscall
--
2.7.0