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[3.16.y-ckt,stable] Patch "x86, tls, ldt: Stop checking lm in LDT_empty" has been added to staging queue

Message ID 1422877846-24523-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Feb. 2, 2015, 11:50 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    x86, tls, ldt: Stop checking lm in LDT_empty

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-ckt6.

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

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From 91327c37f3ce0d9bfb702b38e8161e800660b550 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 22 Jan 2015 11:27:58 -0800
Subject: x86, tls, ldt: Stop checking lm in LDT_empty

commit e30ab185c490e9a9381385529e0fd32f0a399495 upstream.

32-bit programs don't have an lm bit in their ABI, so they can't
reliably cause LDT_empty to return true without resorting to memset.
They shouldn't need to do this.

This should fix a longstanding, if minor, issue in all 64-bit kernels
as well as a potential regression in the TLS hardening code.

Fixes: 41bdc78544b8 x86/tls: Validate TLS entries to protect espfix
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: torvalds@linux-foundation.org
Link: http://lkml.kernel.org/r/72a059de55e86ad5e2935c80aa91880ddf19d07c.1421954363.git.luto@amacapital.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 arch/x86/include/asm/desc.h | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

--
2.1.4
diff mbox

Patch

diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 50d033a8947d..fc237fd0259a 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -251,7 +251,8 @@  static inline void native_load_tls(struct thread_struct *t, unsigned int cpu)
 		gdt[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i];
 }

-#define _LDT_empty(info)				\
+/* This intentionally ignores lm, since 32-bit apps don't have that field. */
+#define LDT_empty(info)					\
 	((info)->base_addr		== 0	&&	\
 	 (info)->limit			== 0	&&	\
 	 (info)->contents		== 0	&&	\
@@ -261,12 +262,6 @@  static inline void native_load_tls(struct thread_struct *t, unsigned int cpu)
 	 (info)->seg_not_present	== 1	&&	\
 	 (info)->useable		== 0)

-#ifdef CONFIG_X86_64
-#define LDT_empty(info) (_LDT_empty(info) && ((info)->lm == 0))
-#else
-#define LDT_empty(info) (_LDT_empty(info))
-#endif
-
 static inline void clear_LDT(void)
 {
 	set_ldt(NULL, 0);