linux-kernel - [PATCH 30/43] x86/mm/kaiser: Map espfix structures

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20171124091448.7649-31-mingo@kernel.org>
Date:   Fri, 24 Nov 2017 10:14:35 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 30/43] x86/mm/kaiser: Map espfix structures

From: Dave Hansen <dave.hansen@...ux.intel.com>

There is some rather arcane code to help when an IRET returns
to 16-bit segments.  It is referred to as the "espfix" code.
This consists of a few per-cpu variables:

	espfix_stack: tells us where the stack is allocated
		      (the bottom)
	espfix_waddr: tells us to where %rsp may be pointed
		      (the top)

These are in addition to the stack itself.  All three things must
be mapped for the espfix code to function.

Note: the espfix code runs with a kernel GSBASE, but user
(shadow) page tables.  A switch to the kernel page tables could
be performed instead of mapping these structures, but mapping
them is simpler and less likely to break the assembly.  To switch
over to the kernel copy, additional temporary storage would be
required which is in short supply in this context.

The original KAISER patch missed this case.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Daniel Gruss <daniel.gruss@...k.tugraz.at>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Kees Cook <keescook@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael Schwarz <michael.schwarz@...k.tugraz.at>
Cc: Moritz Lipp <moritz.lipp@...k.tugraz.at>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Richard Fellner <richard.fellner@...dent.tugraz.at>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-mm@...ck.org
Link: http://lkml.kernel.org/r/20171123003457.EB854D0D@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/espfix_64.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c
index 4780dba2cc59..8bb116d73aaa 100644
--- a/arch/x86/kernel/espfix_64.c
+++ b/arch/x86/kernel/espfix_64.c
@@ -33,6 +33,7 @@
 
 #include <linux/init.h>
 #include <linux/init_task.h>
+#include <linux/kaiser.h>
 #include <linux/kernel.h>
 #include <linux/percpu.h>
 #include <linux/gfp.h>
@@ -41,7 +42,6 @@
 #include <asm/pgalloc.h>
 #include <asm/setup.h>
 #include <asm/espfix.h>
-#include <asm/kaiser.h>
 
 /*
  * Note: we only need 6*8 = 48 bytes for the espfix stack, but round
@@ -61,8 +61,8 @@
 #define PGALLOC_GFP (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO)
 
 /* This contains the *bottom* address of the espfix stack */
-DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack);
-DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr);
+DEFINE_PER_CPU_USER_MAPPED(unsigned long, espfix_stack);
+DEFINE_PER_CPU_USER_MAPPED(unsigned long, espfix_waddr);
 
 /* Initialization mutex - should this be a spinlock? */
 static DEFINE_MUTEX(espfix_init_mutex);
@@ -225,4 +225,10 @@ void init_espfix_ap(int cpu)
 	per_cpu(espfix_stack, cpu) = addr;
 	per_cpu(espfix_waddr, cpu) = (unsigned long)stack_page
 				      + (addr & ~PAGE_MASK);
+	/*
+	 * _PAGE_GLOBAL is not really required.  This is not a hot
+	 * path, but we do it here for consistency.
+	 */
+	kaiser_add_mapping((unsigned long)stack_page, PAGE_SIZE,
+			__PAGE_KERNEL | _PAGE_GLOBAL);
 }
-- 
2.14.1