]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
[PATCH] vdso: randomize the i386 vDSO by moving it into a vma
authorIngo Molnar <mingo@elte.hu>
Tue, 27 Jun 2006 09:53:50 +0000 (02:53 -0700)
committerLinus Torvalds <torvalds@g5.osdl.org>
Wed, 28 Jun 2006 00:32:38 +0000 (17:32 -0700)
commite6e5494cb23d1933735ee47cc674ffe1c4afed6f
treec8945bb3ae5bec38693d801fb589d22d48d6f8eb
parentd5fb34261dcd32c9cb3b28121fdc46308db513a1
[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>
18 files changed:
Documentation/kernel-parameters.txt
arch/i386/Kconfig
arch/i386/kernel/asm-offsets.c
arch/i386/kernel/entry.S
arch/i386/kernel/signal.c
arch/i386/kernel/sysenter.c
arch/i386/kernel/vsyscall-sysenter.S
arch/i386/kernel/vsyscall.lds.S
fs/proc/task_mmu.c
include/asm-i386/elf.h
include/asm-i386/fixmap.h
include/asm-i386/mmu.h
include/asm-i386/page.h
include/asm-i386/thread_info.h
include/asm-i386/unwind.h
include/linux/mm.h
include/linux/sysctl.h
kernel/sysctl.c