Commit-ID: 11bf9b865898961cee60a41c483c9f27ec76e12e Gitweb: http://git.kernel.org/tip/11bf9b865898961cee60a41c483c9f27ec76e12e Author: David Brown <david.br...@linaro.org> AuthorDate: Wed, 17 Feb 2016 14:41:18 -0800 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 22 Feb 2016 08:51:39 +0100
ARM/vdso: Mark the vDSO code read-only after init 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 class on ARM as well 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.br...@linaro.org> Signed-off-by: Kees Cook <keesc...@chromium.org> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Arnd Bergmann <a...@arndb.de> Cc: Borislav Petkov <b...@alien8.de> Cc: Brad Spengler <spen...@grsecurity.net> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Emese Revfy <re.em...@gmail.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mathias Krause <mini...@googlemail.com> Cc: Michael Ellerman <m...@ellerman.id.au> Cc: Nathan Lynch <nathan_ly...@mentor.com> Cc: PaX Team <pagee...@freemail.hu> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Russell King <li...@arm.linux.org.uk> Cc: Thomas Gleixner <t...@linutronix.de> Cc: kernel-harden...@lists.openwall.com Cc: linux-arch <linux-a...@vger.kernel.org> Cc: linux-arm-ker...@lists.infradead.org Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1455748879-21872-8-git-send-email-keesc...@chromium.org Signed-off-by: Ingo Molnar <mi...@kernel.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 b2b97e3..a62a7b6 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"
