From: Kees Cook <keescook@chromium.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>,
David Brown <david.brown@linaro.org>,
Andy Lutomirski <luto@amacapital.net>,
"H. Peter Anvin" <hpa@zytor.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Mathias Krause <minipli@googlemail.com>,
Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, Arnd Bergmann <arnd@arndb.de>,
PaX Team <pageexec@freemail.hu>, Emese Revfy <re.emese@gmail.com>,
kernel-hardening@lists.openwall.com,
linux-kernel@vger.kernel.org,
linux-arch <linux-arch@vger.kernel.org>
Subject: [kernel-hardening] [PATCH v5 7/7] ARM: vdso: Mark vDSO code as read-only
Date: Wed, 17 Feb 2016 14:41:18 -0800 [thread overview]
Message-ID: <1455748879-21872-8-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1455748879-21872-1-git-send-email-keescook@chromium.org>
From: David Brown <david.brown@linaro.org>
Although the arm vDSO is cleanly separated by code/data with the code
being read-only in userspace mappings, the code page is still writable
from the kernel. There have been exploits (such as
http://itszn.com/blog/?p=21) that take advantage of this on x86 to go
from a bad kernel write to full root.
Prevent this specific exploit on arm by putting the vDSO code page in
post-init read-only memory as well.
Before:
vdso: 1 text pages at base 80927000
root@Vexpress:/ cat /sys/kernel/debug/kernel_page_tables
---[ Modules ]---
---[ Kernel Mapping ]---
0x80000000-0x80100000 1M RW NX SHD
0x80100000-0x80600000 5M ro x SHD
0x80600000-0x80800000 2M ro NX SHD
0x80800000-0xbe000000 984M RW NX SHD
After:
vdso: 1 text pages at base 8072b000
root@Vexpress:/ cat /sys/kernel/debug/kernel_page_tables
---[ Modules ]---
---[ Kernel Mapping ]---
0x80000000-0x80100000 1M RW NX SHD
0x80100000-0x80600000 5M ro x SHD
0x80600000-0x80800000 2M ro NX SHD
0x80800000-0xbe000000 984M RW NX SHD
Inspired by https://lkml.org/lkml/2016/1/19/494 based on work by the
PaX Team, Brad Spengler, and Kees Cook.
Signed-off-by: David Brown <david.brown@linaro.org>
Acked-by: Kees Cook <keescook@chromium.org>
---
arch/arm/vdso/vdso.S | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/arm/vdso/vdso.S b/arch/arm/vdso/vdso.S
index b2b97e3e7bab..a62a7b64f49c 100644
--- a/arch/arm/vdso/vdso.S
+++ b/arch/arm/vdso/vdso.S
@@ -23,9 +23,8 @@
#include <linux/const.h>
#include <asm/page.h>
- __PAGE_ALIGNED_DATA
-
.globl vdso_start, vdso_end
+ .section .data..ro_after_init
.balign PAGE_SIZE
vdso_start:
.incbin "arch/arm/vdso/vdso.so"
--
2.6.3
prev parent reply other threads:[~2016-02-17 22:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-17 22:41 [kernel-hardening] [PATCH v5 0/7] introduce post-init read-only memory Kees Cook
2016-02-17 22:41 ` [kernel-hardening] [PATCH v5 1/7] asm-generic: consolidate mark_rodata_ro() Kees Cook
2016-02-19 14:38 ` [kernel-hardening] " Will Deacon
2016-02-17 22:41 ` [kernel-hardening] [PATCH v5 2/7] init: create cmdline param to disable readonly Kees Cook
2016-02-17 22:41 ` [kernel-hardening] [PATCH v5 3/7] x86: make CONFIG_DEBUG_RODATA non-optional Kees Cook
2016-02-17 22:41 ` [kernel-hardening] [PATCH v5 4/7] introduce post-init read-only memory Kees Cook
2016-03-07 13:00 ` [kernel-hardening] " Christian Borntraeger
2016-03-08 0:16 ` Kees Cook
2016-03-08 0:23 ` Andy Lutomirski
2016-02-17 22:41 ` [kernel-hardening] [PATCH v5 5/7] lkdtm: verify that __ro_after_init works correctly Kees Cook
2016-02-17 22:41 ` [kernel-hardening] [PATCH v5 6/7] x86, vdso: mark vDSO read-only after init Kees Cook
2016-02-17 22:41 ` Kees Cook [this message]
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