pulled&pushed.

Thanks!

On 03/22/2016 04:16 AM, David Brown wrote:

commit 88d8a7994e564d209d4b2583496631c2357d386b upstream.

Although the arm64 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 arm64 by putting the vDSO code page in read-only memory as well.

Before the change: [ 3.138366] vdso: 2 pages (1 code @ ffffffc000a71000, 1 data @ ffffffc000a70000) ---[ Kernel Mapping ]--- 0xffffffc000000000-0xffffffc000082000 520K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000082000-0xffffffc000200000 1528K ro x SHD AF UXN MEM/NORMAL 0xffffffc000200000-0xffffffc000800000 6M ro x SHD AF BLK UXN MEM/NORMAL 0xffffffc000800000-0xffffffc0009b6000 1752K ro x SHD AF UXN MEM/NORMAL 0xffffffc0009b6000-0xffffffc000c00000 2344K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000c00000-0xffffffc008000000 116M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc00c000000-0xffffffc07f000000 1840M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc800000000-0xffffffc840000000 1G RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc840000000-0xffffffc87ae00000 942M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87ae00000-0xffffffc87ae70000 448K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af80000-0xffffffc87af8a000 40K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af8b000-0xffffffc87b000000 468K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87b000000-0xffffffc87fe00000 78M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87fe00000-0xffffffc87ff50000 1344K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87ff90000-0xffffffc87ffa0000 64K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87fff0000-0xffffffc880000000 64K RW NX SHD AF UXN MEM/NORMAL

After: [ 3.138368] vdso: 2 pages (1 code @ ffffffc0006de000, 1 data @ ffffffc000a74000) ---[ Kernel Mapping ]--- 0xffffffc000000000-0xffffffc000082000 520K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000082000-0xffffffc000200000 1528K ro x SHD AF UXN MEM/NORMAL 0xffffffc000200000-0xffffffc000800000 6M ro x SHD AF BLK UXN MEM/NORMAL 0xffffffc000800000-0xffffffc0009b8000 1760K ro x SHD AF UXN MEM/NORMAL 0xffffffc0009b8000-0xffffffc000c00000 2336K RW NX SHD AF UXN MEM/NORMAL 0xffffffc000c00000-0xffffffc008000000 116M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc00c000000-0xffffffc07f000000 1840M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc800000000-0xffffffc840000000 1G RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc840000000-0xffffffc87ae00000 942M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87ae00000-0xffffffc87ae70000 448K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af80000-0xffffffc87af8a000 40K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87af8b000-0xffffffc87b000000 468K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87b000000-0xffffffc87fe00000 78M RW NX SHD AF BLK UXN MEM/NORMAL 0xffffffc87fe00000-0xffffffc87ff50000 1344K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87ff90000-0xffffffc87ffa0000 64K RW NX SHD AF UXN MEM/NORMAL 0xffffffc87fff0000-0xffffffc880000000 64K RW NX SHD AF UXN MEM/NORMAL

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: Will Deacon will.deacon@arm.com Acked-by: Ard Biesheuvel ard.biesheuvel@linaro.org [catalin.marinas@arm.com: removed superfluous __PAGE_ALIGNED_DATA] Signed-off-by: Catalin Marinas catalin.marinas@arm.com

---

arch/arm64/kernel/vdso/vdso.S | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/vdso/vdso.S b/arch/arm64/kernel/vdso/vdso.S index 60c1db5..82379a7 100644 --- a/arch/arm64/kernel/vdso/vdso.S +++ b/arch/arm64/kernel/vdso/vdso.S @@ -21,9 +21,8 @@ #include <linux/const.h> #include <asm/page.h>

• __PAGE_ALIGNED_DATA
• .globl vdso_start, vdso_end

• .section .rodata .balign PAGE_SIZE

vdso_start: .incbin "arch/arm64/kernel/vdso/vdso.so"