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From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@mit.edu>,
	x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, Jesper Juhl <jj@chaosbits.net>,
	Borislav Petkov <bp@alien8.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arjan van de Ven <arjan@infradead.org>,
	Jan Beulich <JBeulich@novell.com>,
	richard -rw- weinberger <richard.weinberger@gmail.com>,
	Mikael Pettersson <mikpe@it.uu.se>,
	Andi Kleen <andi@firstfloor.org>, Brian Gerst <brgerst@gmail.com>,
	Louis Rilling <Louis.Rilling@kerlabs.com>,
	Valdis.Kletnieks@vt.edu, pageexec@freemail.hu
Subject: [PATCH] x86-64, vsyscalls: Rename UNSAFE_VSYSCALLS to COMPAT_VSYSCALLS
Date: Mon, 6 Jun 2011 12:24:19 +0200
Message-ID: <20110606102419.GA837@elte.hu> (raw)
In-Reply-To: <BANLkTimrhO8QfBqQsH_Q13ghRH2P+ZP7AA@mail.gmail.com>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Mon, Jun 6, 2011 at 2:50 AM, Andy Lutomirski <luto@mit.edu> wrote:
> > CONFIG_UNSAFE_VSYSCALLS was added in the previous patch as a
> > temporary hack to avoid penalizing users who don't build glibc from
> > git.
> 
> I really hate that name.
> 
> Do you have *any* reason to call this "unsafe"?

No, there's no reason at all for that. That naming is borderline 
security FUD and last time i saw the series i considered renaming
it but got distracted :-)

How about the patch below? COMPAT_VSYSCALLS looks like a good logical 
extension to the COMPAT_VDSO we already have.

CONFIG_FIXED_VSYSCALLS seemed a bit awkward to me nor does it carry 
the compat nature of them.

Thanks,

	Ingo

--------------->
>From 1593843e2ada6d6832d0de4d633aacd997dc3a45 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Mon, 6 Jun 2011 12:13:40 +0200
Subject: [PATCH] x86-64, vsyscalls: Rename UNSAFE_VSYSCALLS to COMPAT_VSYSCALLS

Linus pointed out that the UNSAFE_VSYSCALL naming was inherently
bad: it suggests that there's something unsafe about enabling them,
while in reality they only have any security effect in the presence
of some *other* security hole.

So rename it to CONFIG_COMPAT_VSYSCALL and fix the documentation
and Kconfig text to correctly explain the purpose of this change.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@mit.edu>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: richard -rw- weinberger <richard.weinberger@gmail.com>
Cc: Mikael Pettersson <mikpe@it.uu.se>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: Valdis.Kletnieks@vt.edu
Cc: pageexec@freemail.hu
Link: http://lkml.kernel.org/r/BANLkTimrhO8QfBqQsH_Q13ghRH2P%2BZP7AA@mail.gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 Documentation/feature-removal-schedule.txt |    7 ++++---
 arch/x86/Kconfig                           |   17 ++++++++++-------
 arch/x86/kernel/vsyscall_64.c              |    8 ++++----
 arch/x86/kernel/vsyscall_emu_64.S          |    2 +-
 4 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 94b4470..4282ab2 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -601,10 +601,11 @@ Who:	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 
 ----------------------------
 
-What:	CONFIG_UNSAFE_VSYSCALLS (x86_64)
+What:	CONFIG_COMPAT_VSYSCALLS (x86_64)
 When:	When glibc 2.14 or newer is ubitquitous.  Perhaps mid-2012.
-Why:	Having user-executable code at a fixed address is a security problem.
-	Turning off CONFIG_UNSAFE_VSYSCALLS mostly removes the risk but will
+Why:	Having user-executable syscall invoking code at a fixed addresses makes
+	it easier for attackers to exploit security holes.
+	Turning off CONFIG_COMPAT_VSYSCALLS mostly removes the risk but will
 	make the time() function slower on glibc versions 2.13 and below.
 Who:	Andy Lutomirski <luto@mit.edu>
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 79e5d8a..30041d8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1646,20 +1646,23 @@ config COMPAT_VDSO
 
 	  If unsure, say Y.
 
-config UNSAFE_VSYSCALLS
+config COMPAT_VSYSCALLS
 	def_bool y
-	prompt "Unsafe fast legacy vsyscalls"
+	prompt "Fixed address legacy vsyscalls"
 	depends on X86_64
 	---help---
 	  Legacy user code expects to be able to issue three syscalls
-	  by calling fixed addresses in kernel space.  If you say N,
-	  then the kernel traps and emulates these calls.  If you say
-	  Y, then there is actual executable code at a fixed address
-	  to implement time() efficiently.
+	  by calling a fixed addresses.  If you say N, then the kernel
+	  traps and emulates these calls.  If you say Y, then there is
+	  actual executable code at a fixed address to implement time()
+	  efficiently.
 
 	  On a system with recent enough glibc (probably 2.14 or
 	  newer) and no static binaries, you can say N without a
-	  performance penalty to improve security
+	  performance penalty to improve security: having no fixed
+	  address userspace-executable syscall invoking code makes
+	  it harder for both remote and local attackers to exploit
+	  security holes.
 
 	  If unsure, say Y.
 
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 285af7a..27d49b7 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -116,7 +116,7 @@ static int al_to_vsyscall_nr(u8 al)
 	return -1;
 }
 
-#ifdef CONFIG_UNSAFE_VSYSCALLS
+#ifdef CONFIG_COMPAT_VSYSCALLS
 
 /* This will break when the xtime seconds get inaccurate, but that is
  * unlikely */
@@ -138,9 +138,9 @@ vtime(time_t *t)
 	return result;
 }
 
-#endif /* CONFIG_UNSAFE_VSYSCALLS */
+#endif /* CONFIG_COMPAT_VSYSCALLS */
 
-/* If CONFIG_UNSAFE_VSYSCALLS=y, then this is incorrect for vsyscall_nr == 1. */
+/* If CONFIG_COMPAT_VSYSCALLS=y, then this is incorrect for vsyscall_nr == 1. */
 static inline unsigned long vsyscall_intcc_addr(int vsyscall_nr)
 {
 	return VSYSCALL_START + 1024*vsyscall_nr + 2;
@@ -202,7 +202,7 @@ void dotraplinkage do_emulate_vsyscall(struct pt_regs *regs, long error_code)
 		break;
 
 	case 1:
-#ifdef CONFIG_UNSAFE_VSYSCALLS
+#ifdef CONFIG_COMPAT_VSYSCALLS
 		warn_bad_vsyscall(KERN_WARNING, regs, "bogus time() vsyscall "
 				  "emulation (exploit attempt?)");
 		goto sigsegv;
diff --git a/arch/x86/kernel/vsyscall_emu_64.S b/arch/x86/kernel/vsyscall_emu_64.S
index 7ebde61..2d53e26 100644
--- a/arch/x86/kernel/vsyscall_emu_64.S
+++ b/arch/x86/kernel/vsyscall_emu_64.S
@@ -25,7 +25,7 @@ ENTRY(vsyscall_0)
 	ret
 END(vsyscall_0)
 
-#ifndef CONFIG_UNSAFE_VSYSCALLS
+#ifndef CONFIG_COMPAT_VSYSCALLS
 .section .vsyscall_1, "a"
 ENTRY(vsyscall_1)
 	movb $0xce, %al

  parent reply index

Thread overview: 112+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-05 17:50 [PATCH v5 0/9] Remove syscall instructions at fixed addresses Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 1/9] x86-64: Fix alignment of jiffies variable Andy Lutomirski
2011-06-06  8:31   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 2/9] x86-64: Document some of entry_64.S Andy Lutomirski
2011-06-06  8:31   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 3/9] x86-64: Give vvars their own page Andy Lutomirski
2011-06-06  8:32   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 4/9] x86-64: Remove kernel.vsyscall64 sysctl Andy Lutomirski
2011-06-06  8:32   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-12-05 18:27   ` [PATCH v5 4/9] " Matthew Maurer
2011-06-05 17:50 ` [PATCH v5 5/9] x86-64: Map the HPET NX Andy Lutomirski
2011-06-06  8:33   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 6/9] x86-64: Remove vsyscall number 3 (venosys) Andy Lutomirski
2011-06-06  8:33   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 7/9] x86-64: Fill unused parts of the vsyscall page with 0xcc Andy Lutomirski
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls Andy Lutomirski
2011-06-05 19:30   ` Ingo Molnar
2011-06-05 20:01     ` Andrew Lutomirski
2011-06-06  7:39       ` Ingo Molnar
2011-06-06  9:42       ` pageexec
2011-06-06 11:19         ` Andrew Lutomirski
2011-06-06 11:56           ` pageexec
2011-06-06 12:43             ` Andrew Lutomirski
2011-06-06 13:58               ` pageexec
2011-06-06 14:07                 ` Brian Gerst
2011-06-07 23:32                   ` pageexec
2011-06-07 23:49                     ` Andrew Lutomirski
2011-06-08  6:32                       ` pageexec
2011-06-06 15:26                 ` Ingo Molnar
2011-06-06 15:48                   ` pageexec
2011-06-06 15:59                     ` Ingo Molnar
2011-06-06 16:19                       ` pageexec
2011-06-06 16:47                         ` Ingo Molnar
2011-06-06 22:49                           ` pageexec
2011-06-06 22:57                             ` david
2011-06-07  9:07                               ` Ingo Molnar
2011-06-07  6:59                             ` Pekka Enberg
2011-06-07  8:30                             ` Ingo Molnar
2011-06-07 23:24                               ` pageexec
2011-06-08  5:55                                 ` Pekka Enberg
2011-06-08  6:19                                   ` pageexec
2011-06-08  6:48                                 ` Ingo Molnar
2011-06-08  9:02                                   ` pageexec
2011-06-08  9:11                                     ` Andi Kleen
2011-06-08  9:35                                       ` pageexec
2011-06-08 10:06                                         ` Andi Kleen
2011-06-08 10:26                                           ` pageexec
2011-06-08 10:39                                             ` Ingo Molnar
2011-06-08 10:35                                           ` Ingo Molnar
2011-06-08  9:15                                     ` Ingo Molnar
2011-06-08  7:16                                 ` Ingo Molnar
2011-06-08  9:29                                   ` pageexec
2011-06-06 14:01             ` Linus Torvalds
2011-06-06 14:55               ` pageexec
2011-06-06 15:33                 ` Ingo Molnar
2011-06-06 15:58                   ` pageexec
2011-06-06 15:41         ` Ingo Molnar
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-06  8:35   ` [tip:x86/vdso] x86-64, vdso, seccomp: Fix !CONFIG_SECCOMP build tip-bot for Ingo Molnar
2011-06-07  7:49   ` [tip:x86/vdso] x86-64: Emulate legacy vsyscalls tip-bot for Andy Lutomirski
2011-06-07  8:03   ` tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule Andy Lutomirski
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-06  8:46   ` [PATCH v5 9/9] " Linus Torvalds
2011-06-06  9:31     ` Andi Kleen
2011-06-06 10:39       ` pageexec
2011-06-06 13:56         ` Linus Torvalds
2011-06-06 18:46           ` pageexec
2011-06-06 20:40             ` Linus Torvalds
2011-06-06 20:51               ` Andrew Lutomirski
2011-06-06 21:54                 ` Ingo Molnar
2011-06-06 21:45               ` Ingo Molnar
2011-06-06 21:48                 ` Ingo Molnar
     [not found]                 ` <BANLkTi==uw_h78oaep1cCOCzwY0edLUU_Q@mail.gmail.com>
2011-06-07  8:03                   ` [PATCH, v6] x86-64: Emulate legacy vsyscalls Ingo Molnar
2011-06-06 21:53               ` [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule pageexec
2011-06-06 14:44         ` Ingo Molnar
2011-06-06 15:01           ` pageexec
2011-06-06 15:15             ` Ingo Molnar
2011-06-06 15:29               ` pageexec
2011-06-06 16:54                 ` Ingo Molnar
2011-06-06 18:59           ` pageexec
2011-06-06 19:25             ` Ingo Molnar
2011-06-07  0:34               ` pageexec
2011-06-07  9:51                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-10 11:19                     ` Ingo Molnar
2011-06-14  0:48                       ` pageexec
2011-06-15 19:42                         ` Valdis.Kletnieks
2011-06-06 14:52         ` Ingo Molnar
2011-06-06 10:24     ` Ingo Molnar [this message]
2011-06-06 11:20       ` [PATCH] x86-64, vsyscalls: Rename UNSAFE_VSYSCALLS to COMPAT_VSYSCALLS pageexec
2011-06-06 12:47         ` Ingo Molnar
2011-06-06 12:48           ` Ingo Molnar
2011-06-06 18:04           ` pageexec
2011-06-06 19:12             ` Ingo Molnar
2011-06-07  0:02               ` pageexec
2011-06-07  9:56                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-09  6:48                     ` Ingo Molnar
2011-06-09 23:33                       ` pageexec
2011-06-07 10:05                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-09  7:02                     ` Ingo Molnar
2011-06-09 23:33                       ` pageexec
2011-06-07 10:13                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-06 12:19       ` Ted Ts'o
2011-06-06 12:33         ` Andrew Lutomirski
2011-06-06 12:37         ` Ingo Molnar
2011-06-06 14:34     ` [tip:x86/vdso] " tip-bot for Ingo Molnar
2011-06-05 20:05 ` [PATCH v5 0/9] Remove syscall instructions at fixed addresses Andrew Lutomirski

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