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Groups > linux.kernel > #1331531
| From | David Brown <david.brown@linaro.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH] arm64: vdso: Mark vDSO code as read-only |
| Date | 2016-02-10 23:00 +0100 |
| Message-ID | <r0KXM-7U9-13@gated-at.bofh.it> (permalink) |
| Organization | linux.* mail to news gateway |
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> --- arch/arm64/kernel/vdso/vdso.S | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/kernel/vdso/vdso.S b/arch/arm64/kernel/vdso/vdso.S index 60c1db5..db7c0f2 100644 --- a/arch/arm64/kernel/vdso/vdso.S +++ b/arch/arm64/kernel/vdso/vdso.S @@ -24,6 +24,7 @@ __PAGE_ALIGNED_DATA .globl vdso_start, vdso_end + .section .rodata .balign PAGE_SIZE vdso_start: .incbin "arch/arm64/kernel/vdso/vdso.so" -- 2.7.1
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[PATCH] arm64: vdso: Mark vDSO code as read-only David Brown <david.brown@linaro.org> - 2016-02-10 23:00 +0100
Re: [PATCH] arm64: vdso: Mark vDSO code as read-only Will Deacon <will.deacon@arm.com> - 2016-02-11 14:50 +0100
Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-11 15:20 +0100
Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only David Brown <david.brown@linaro.org> - 2016-02-13 01:40 +0100
Re: [kernel-hardening] [PATCH] arm64: vdso: Mark vDSO code as read-only Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-13 10:10 +0100
Re: [PATCH] arm64: vdso: Mark vDSO code as read-only Catalin Marinas <catalin.marinas@arm.com> - 2016-02-16 19:30 +0100
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