x86/vsyscall/64: Drop "native" vsyscalls
Since Linux v3.2, vsyscalls have been deprecated and slow. From v3.2
on, Linux had three vsyscall modes: "native", "emulate", and "none".
"emulate" is the default. All known user programs work correctly in
emulate mode, but vsyscalls turn into page faults and are emulated.
This is very slow. In "native" mode, the vsyscall page is easily
usable as an exploit gadget, but vsyscalls are a bit faster -- they
turn into normal syscalls. (This is in contrast to vDSO functions,
which can be much faster than syscalls.) In "none" mode, there are
no vsyscalls.
For all practical purposes, "native" was really just a chicken bit
in case something went wrong with the emulation. It's been over six
years, and nothing has gone wrong. Delete it.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Kernel Hardening <kernel-hardening@lists.openwall.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/519fee5268faea09ae550776ce969fa6e88668b0.1520449896.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c1aed6c..09c599e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2266,7 +2266,7 @@
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].
+ line parameter vsyscall=[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
@@ -2274,15 +2274,6 @@
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