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| Started by | tip-bot for Kees Cook <tipbot@zytor.com> |
|---|---|
| First post | 2015-09-20 13:40 +0200 |
| Last post | 2015-09-21 10:10 +0200 |
| Articles | 3 — 3 participants |
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[tip:x86/asm] x86/entry/vsyscall: Add CONFIG to control default tip-bot for Kees Cook <tipbot@zytor.com> - 2015-09-20 13:40 +0200
Re: [tip:x86/asm] x86/entry/vsyscall: Add CONFIG to control default Borislav Petkov <bp@alien8.de> - 2015-09-21 09:50 +0200
[tip:x86/asm] x86/entry/vsyscall: Fix undefined symbol warning tip-bot for Borislav Petkov <tipbot@zytor.com> - 2015-09-21 10:10 +0200
| From | tip-bot for Kees Cook <tipbot@zytor.com> |
|---|---|
| Date | 2015-09-20 13:40 +0200 |
| Subject | [tip:x86/asm] x86/entry/vsyscall: Add CONFIG to control default |
| Message-ID | <qaL8m-72O-9@gated-at.bofh.it> |
Commit-ID: 3dc33bd30f3e1c1bcaaafa3482737694debf0f0b
Gitweb: http://git.kernel.org/tip/3dc33bd30f3e1c1bcaaafa3482737694debf0f0b
Author: Kees Cook <keescook@chromium.org>
AuthorDate: Wed, 12 Aug 2015 17:55:19 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 20 Sep 2015 10:31:06 +0200
x86/entry/vsyscall: Add CONFIG to control default
Most modern systems can run with vsyscall=none. In an effort to
provide a way for build-time defaults to lack legacy settings,
this adds a new CONFIG to select the type of vsyscall mapping to
use, similar to the existing "vsyscall" command line parameter.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150813005519.GA11696@www.outflux.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/Kconfig | 49 +++++++++++++++++++++++++++++++++++
arch/x86/entry/vsyscall/vsyscall_64.c | 9 ++++++-
2 files changed, 57 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 328c835..9bfb9e1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2042,6 +2042,55 @@ config COMPAT_VDSO
If unsure, say N: if you are compiling your own kernel, you
are unlikely to be using a buggy version of glibc.
+choice
+ prompt "vsyscall table for legacy applications"
+ depends on X86_64
+ default LEGACY_VSYSCALL_EMULATE
+ help
+ Legacy user code that does not know how to find the vDSO expects
+ to be able to issue three syscalls by calling fixed addresses in
+ kernel space. Since this location is not randomized with ASLR,
+ it can be used to assist security vulnerability exploitation.
+
+ This setting can be changed at boot time via the kernel command
+ line parameter vsyscall=[native|emulate|none].
+
+ On a system with recent enough glibc (2.14 or newer) and no
+ static binaries, you can say None without a performance penalty
+ to improve security.
+
+ If unsure, select "Emulate".
+
+ config LEGACY_VSYSCALL_NATIVE
+ bool "Native"
+ help
+ Actual executable code is located in the fixed vsyscall
+ address mapping, implementing time() efficiently. Since
+ this makes the mapping executable, it can be used during
+ security vulnerability exploitation (traditionally as
+ ROP gadgets). This configuration is not recommended.
+
+ config LEGACY_VSYSCALL_EMULATE
+ bool "Emulate"
+ help
+ The kernel traps and emulates calls into the fixed
+ vsyscall address mapping. This makes the mapping
+ non-executable, but it still contains known contents,
+ which could be used in certain rare security vulnerability
+ exploits. This configuration is recommended when userspace
+ still uses the vsyscall area.
+
+ config LEGACY_VSYSCALL_NONE
+ bool "None"
+ help
+ There will be no vsyscall mapping at all. This will
+ eliminate any risk of ASLR bypass due to the vsyscall
+ fixed address mapping. Attempts to use the vsyscalls
+ will be reported to dmesg, so that either old or
+ malicious userspace programs can be identified.
+
+endchoice
+
config CMDLINE_BOOL
bool "Built-in kernel command line"
---help---
diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index b160c0c..76e0fd3 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -38,7 +38,14 @@
#define CREATE_TRACE_POINTS
#include "vsyscall_trace.h"
-static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
+static enum { EMULATE, NATIVE, NONE } vsyscall_mode =
+#ifdef CONFIG_LEGACY_VSYSCALL_NATIVE
+ NATIVE;
+#elif CONFIG_LEGACY_VSYSCALL_NONE
+ NONE;
+#else
+ EMULATE;
+#endif
static int __init vsyscall_setup(char *str)
{
--
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| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Date | 2015-09-21 09:50 +0200 |
| Message-ID | <qb41l-cd-29@gated-at.bofh.it> |
| In reply to | #1228875 |
On Sun, Sep 20, 2015 at 04:29:18AM -0700, tip-bot for Kees Cook wrote:
> Commit-ID: 3dc33bd30f3e1c1bcaaafa3482737694debf0f0b
> Gitweb: http://git.kernel.org/tip/3dc33bd30f3e1c1bcaaafa3482737694debf0f0b
> Author: Kees Cook <keescook@chromium.org>
> AuthorDate: Wed, 12 Aug 2015 17:55:19 -0700
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Sun, 20 Sep 2015 10:31:06 +0200
>
> x86/entry/vsyscall: Add CONFIG to control default
>
> Most modern systems can run with vsyscall=none. In an effort to
> provide a way for build-time defaults to lack legacy settings,
> this adds a new CONFIG to select the type of vsyscall mapping to
> use, similar to the existing "vsyscall" command line parameter.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Acked-by: Andy Lutomirski <luto@amacapital.net>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Brian Gerst <brgerst@gmail.com>
> Cc: Denys Vlasenko <dvlasenk@redhat.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Link: http://lkml.kernel.org/r/20150813005519.GA11696@www.outflux.net
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> ---
> arch/x86/Kconfig | 49 +++++++++++++++++++++++++++++++++++
> arch/x86/entry/vsyscall/vsyscall_64.c | 9 ++++++-
> 2 files changed, 57 insertions(+), 1 deletion(-)
...
> diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
> index b160c0c..76e0fd3 100644
> --- a/arch/x86/entry/vsyscall/vsyscall_64.c
> +++ b/arch/x86/entry/vsyscall/vsyscall_64.c
> @@ -38,7 +38,14 @@
> #define CREATE_TRACE_POINTS
> #include "vsyscall_trace.h"
>
> -static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
> +static enum { EMULATE, NATIVE, NONE } vsyscall_mode =
> +#ifdef CONFIG_LEGACY_VSYSCALL_NATIVE
> + NATIVE;
> +#elif CONFIG_LEGACY_VSYSCALL_NONE
My gcc complains about this. If it hasn't been fixed yet, here's a fix:
---
From: Borislav Petkov <bp@suse.de>
Date: Mon, 21 Sep 2015 09:34:23 +0200
Subject: [PATCH] x86/entry/vsyscall: Fix undefined symbol warning
3dc33bd30f3e1 ("x86/entry/vsyscall: Add CONFIG to control default") did
the ifdef/elif thing but gcc doesn't like that:
arch/x86/entry/vsyscall/vsyscall_64.c:44:7: warning: "CONFIG_LEGACY_VSYSCALL_NONE" is not defined [-Wundef]
#elif CONFIG_LEGACY_VSYSCALL_NONE
^
Use defined() instead.
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150813005519.GA11696@www.outflux.net
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/entry/vsyscall/vsyscall_64.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 76e0fd3ea1fb..174c2549939d 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -39,9 +39,9 @@
#include "vsyscall_trace.h"
static enum { EMULATE, NATIVE, NONE } vsyscall_mode =
-#ifdef CONFIG_LEGACY_VSYSCALL_NATIVE
+#if defined(CONFIG_LEGACY_VSYSCALL_NATIVE)
NATIVE;
-#elif CONFIG_LEGACY_VSYSCALL_NONE
+#elif defined(CONFIG_LEGACY_VSYSCALL_NONE)
NONE;
#else
EMULATE;
--
2.1.4
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
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| From | tip-bot for Borislav Petkov <tipbot@zytor.com> |
|---|---|
| Date | 2015-09-21 10:10 +0200 |
| Subject | [tip:x86/asm] x86/entry/vsyscall: Fix undefined symbol warning |
| Message-ID | <qb4kG-Od-7@gated-at.bofh.it> |
| In reply to | #1229092 |
Commit-ID: 93f13a9f96771a064c716364aebc6e283b186eb8
Gitweb: http://git.kernel.org/tip/93f13a9f96771a064c716364aebc6e283b186eb8
Author: Borislav Petkov <bp@alien8.de>
AuthorDate: Mon, 21 Sep 2015 09:48:29 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 21 Sep 2015 09:56:59 +0200
x86/entry/vsyscall: Fix undefined symbol warning
Commit:
3dc33bd30f3e1 ("x86/entry/vsyscall: Add CONFIG to control default")
did the ifdef/elif thing but GCC doesn't like that:
arch/x86/entry/vsyscall/vsyscall_64.c:44:7: warning: "CONFIG_LEGACY_VSYSCALL_NONE" is not defined [-Wundef]
#elif CONFIG_LEGACY_VSYSCALL_NONE
^
Use defined() instead.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150921074829.GA3550@pd.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/vsyscall/vsyscall_64.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 76e0fd3..174c254 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -39,9 +39,9 @@
#include "vsyscall_trace.h"
static enum { EMULATE, NATIVE, NONE } vsyscall_mode =
-#ifdef CONFIG_LEGACY_VSYSCALL_NATIVE
+#if defined(CONFIG_LEGACY_VSYSCALL_NATIVE)
NATIVE;
-#elif CONFIG_LEGACY_VSYSCALL_NONE
+#elif defined(CONFIG_LEGACY_VSYSCALL_NONE)
NONE;
#else
EMULATE;
--
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