diff options
| author | Ingo Molnar <mingo@elte.hu> | 2006-06-27 02:53:50 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-06-27 17:32:38 -0700 |
| commit | e6e5494cb23d1933735ee47cc674ffe1c4afed6f (patch) | |
| tree | c8945bb3ae5bec38693d801fb589d22d48d6f8eb /arch/i386/Kconfig | |
| parent | d5fb34261dcd32c9cb3b28121fdc46308db513a1 (diff) | |
[PATCH] vdso: randomize the i386 vDSO by moving it into a vma
Move the i386 VDSO down into a vma and thus randomize it.
Besides the security implications, this feature also helps debuggers, which
can COW a vma-backed VDSO just like a normal DSO and can thus do
single-stepping and other debugging features.
It's good for hypervisors (Xen, VMWare) too, which typically live in the same
high-mapped address space as the VDSO, hence whenever the VDSO is used, they
get lots of guest pagefaults and have to fix such guest accesses up - which
slows things down instead of speeding things up (the primary purpose of the
VDSO).
There's a new CONFIG_COMPAT_VDSO (default=y) option, which provides support
for older glibcs that still rely on a prelinked high-mapped VDSO. Newer
distributions (using glibc 2.3.3 or later) can turn this option off. Turning
it off is also recommended for security reasons: attackers cannot use the
predictable high-mapped VDSO page as syscall trampoline anymore.
There is a new vdso=[0|1] boot option as well, and a runtime
/proc/sys/vm/vdso_enabled sysctl switch, that allows the VDSO to be turned
on/off.
(This version of the VDSO-randomization patch also has working ELF
coredumping, the previous patch crashed in the coredumping code.)
This code is a combined work of the exec-shield VDSO randomization
code and Gerd Hoffmann's hypervisor-centric VDSO patch. Rusty Russell
started this patch and i completed it.
[akpm@osdl.org: cleanups]
[akpm@osdl.org: compile fix]
[akpm@osdl.org: compile fix 2]
[akpm@osdl.org: compile fix 3]
[akpm@osdl.org: revernt MAXMEM change]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Cc: Gerd Hoffmann <kraxel@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/i386/Kconfig')
| -rw-r--r-- | arch/i386/Kconfig | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig index 6662f8c44798..3bb221db164a 100644 --- a/arch/i386/Kconfig +++ b/arch/i386/Kconfig @@ -780,6 +780,17 @@ config HOTPLUG_CPU enable suspend on SMP systems. CPUs can be controlled through /sys/devices/system/cpu. +config COMPAT_VDSO + bool "Compat VDSO support" + default y + help + Map the VDSO to the predictable old-style address too. + ---help--- + Say N here if you are running a sufficiently recent glibc + version (2.3.3 or later), to remove the high-mapped + VDSO mapping and to exclusively use the randomized VDSO. + + If unsure, say Y. endmenu |