Messages in this thread |  | | From | David Woodhouse <> | Subject | [PATCH v8 00/12] Retpoline: Avoid speculative indirect calls in kernel | Date | Thu, 11 Jan 2018 21:46:22 +0000 |
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This is a mitigation for the 'variant 2' attack described in https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html
Using GCC patches available from the hjl/indirect/gcc-7-branch/master branch of https://github.com/hjl-tools/gcc/commits/hjl and by manually patching assembler code, all vulnerable indirect branches (that occur after userspace first runs) are eliminated from the kernel.
They are replaced with a 'retpoline' call sequence which deliberately prevents speculation.
Fedora 27 packages of the updated compiler are available at https://koji.fedoraproject.org/koji/taskinfo?taskID=24065739
v1: Initial post. v2: Add CONFIG_RETPOLINE to build kernel without it. Change warning messages. Hide modpost warning message v3: Update to the latest CET-capable retpoline version Reinstate ALTERNATIVE support v4: Finish reconciling Andi's and my patch sets, bug fixes. Exclude objtool support for now Add 'noretpoline' boot option Add AMD retpoline alternative v5: Silence MODVERSIONS warnings Use pause;jmp loop instead of lfence;jmp Switch to X86_FEATURE_RETPOLINE positive feature logic Emit thunks inline from assembler macros Merge AMD support into initial patch v6: Update to latest GCC patches with no dots in symbols Fix MODVERSIONS properly(ish) Fix typo breaking 32-bit, introduced in V5 Never set X86_FEATURE_RETPOLINE_AMD yet, pending confirmation v7: Further bikeshedding on macro names Stuff RSB on kernel entry Implement 'spectre_v2=' command line option for IBRS/IBPB too Revert to precisely the asm sequences from the Google paper v8: Re-enable (I won't say "fix") objtool support Use numeric labels for GCC compatibility Add support for RSB-stuffing on vmexit I don't know... other bloody bikeshedding. Can I sleep now?
Andi Kleen (1): x86/retpoline/irq32: Convert assembler indirect jumps
David Woodhouse (10): objtool: Allow alternatives to be ignored x86/retpoline: Add initial retpoline support x86/spectre: Add boot time option to select Spectre v2 mitigation x86/retpoline/crypto: Convert crypto assembler indirect jumps x86/retpoline/entry: Convert entry assembler indirect jumps x86/retpoline/ftrace: Convert ftrace assembler indirect jumps x86/retpoline/hyperv: Convert assembler indirect jumps x86/retpoline/xen: Convert Xen hypercall indirect jumps x86/retpoline/checksum32: Convert assembler indirect jumps x86/retpoline: Fill return stack buffer on vmexit
Josh Poimboeuf (1): objtool: Detect jumps to retpoline thunks
Documentation/admin-guide/kernel-parameters.txt | 28 ++++ arch/x86/Kconfig | 13 ++ arch/x86/Makefile | 10 ++ arch/x86/crypto/aesni-intel_asm.S | 5 +- arch/x86/crypto/camellia-aesni-avx-asm_64.S | 3 +- arch/x86/crypto/camellia-aesni-avx2-asm_64.S | 3 +- arch/x86/crypto/crc32c-pcl-intel-asm_64.S | 3 +- arch/x86/entry/entry_32.S | 5 +- arch/x86/entry/entry_64.S | 12 +- arch/x86/include/asm/asm-prototypes.h | 25 +++ arch/x86/include/asm/cpufeatures.h | 2 + arch/x86/include/asm/mshyperv.h | 18 +- arch/x86/include/asm/nospec-branch.h | 209 ++++++++++++++++++++++++ arch/x86/include/asm/xen/hypercall.h | 5 +- arch/x86/kernel/cpu/bugs.c | 158 +++++++++++++++++- arch/x86/kernel/ftrace_32.S | 6 +- arch/x86/kernel/ftrace_64.S | 8 +- arch/x86/kernel/irq_32.c | 9 +- arch/x86/kvm/svm.c | 4 + arch/x86/kvm/vmx.c | 4 + arch/x86/lib/Makefile | 1 + arch/x86/lib/checksum_32.S | 7 +- arch/x86/lib/retpoline.S | 48 ++++++ tools/objtool/check.c | 69 +++++++- tools/objtool/check.h | 2 +- 25 files changed, 616 insertions(+), 41 deletions(-) create mode 100644 arch/x86/include/asm/nospec-branch.h create mode 100644 arch/x86/lib/retpoline.S
-- 2.7.4
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