This is a note to let you know that I've just added the patch titled

x86: Introduce barrier_nospec

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86_Introduce_barrier_nospec.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

Subject: x86: Introduce barrier_nospec From: Dan Williams dan.j.williams@intel.com Date: Mon Jan 29 17:02:33 2018 -0800

From: Dan Williams dan.j.williams@intel.com

commit b3d7ad85b80bbc404635dca80f5b129f6242bc7a

Rename the open coded form of this instruction sequence from rdtsc_ordered() into a generic barrier primitive, barrier_nospec().

One of the mitigations for Spectre variant1 vulnerabilities is to fence speculative execution after successfully validating a bounds check. I.e. force the result of a bounds check to resolve in the instruction pipeline to ensure speculative execution honors that result before potentially operating on out-of-bounds data.

No functional changes.

Suggested-by: Linus Torvalds torvalds@linux-foundation.org Suggested-by: Andi Kleen ak@linux.intel.com Suggested-by: Ingo Molnar mingo@redhat.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: linux-arch@vger.kernel.org Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Kees Cook keescook@chromium.org Cc: kernel-hardening@lists.openwall.com Cc: gregkh@linuxfoundation.org Cc: Al Viro viro@zeniv.linux.org.uk Cc: alan@linux.intel.com Link: https://lkml.kernel.org/r/151727415361.33451.9049453007262764675.stgit@dwill... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/include/asm/barrier.h | 4 ++++ arch/x86/include/asm/msr.h | 3 +-- 2 files changed, 5 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -48,6 +48,10 @@ static inline unsigned long array_index_ /* Override the default implementation from linux/nospec.h. */ #define array_index_mask_nospec array_index_mask_nospec

+/* Prevent speculative execution past this barrier. */ +#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \ + "lfence", X86_FEATURE_LFENCE_RDTSC) + #ifdef CONFIG_X86_PPRO_FENCE #define dma_rmb() rmb() #else --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -214,8 +214,7 @@ static __always_inline unsigned long lon * that some other imaginary CPU is updating continuously with a * time stamp. */ - alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, - "lfence", X86_FEATURE_LFENCE_RDTSC); + barrier_nospec(); return rdtsc(); }

Patches currently in stable-queue which might be from torvalds@linux-foundation.org are

queue-4.14/objtool_Add_support_for_alternatives_at_the_end_of_a_section.patch queue-4.14/x86pti_Do_not_enable_PTI_on_CPUs_which_are_not_vulnerable_to_Meltdown.patch queue-4.14/x86_Introduce_barrier_nospec.patch queue-4.14/x86speculation_Use_Indirect_Branch_Prediction_Barrier_in_context_switch.patch queue-4.14/x86get_user_Use_pointer_masking_to_limit_speculation.patch queue-4.14/x86_Introduce___uaccess_begin_nospec()_and_uaccess_try_nospec.patch queue-4.14/x86cpufeature_Blacklist_SPEC_CTRLPRED_CMD_on_early_Spectre_v2_microcodes.patch queue-4.14/x86cpufeatures_Add_Intel_feature_bits_for_Speculation_Control.patch queue-4.14/x86paravirt_Remove_noreplace-paravirt_cmdline_option.patch queue-4.14/KVM_VMX_Make_indirect_call_speculation_safe.patch queue-4.14/x86msr_Add_definitions_for_new_speculation_control_MSRs.patch queue-4.14/x86alternative_Print_unadorned_pointers.patch queue-4.14/KVMVMX_Allow_direct_access_to_MSR_IA32_SPEC_CTRL.patch queue-4.14/x86cpufeatures_Add_CPUID_7_EDX_CPUID_leaf.patch queue-4.14/array_index_nospec_Sanitize_speculative_array_de-references.patch queue-4.14/Documentation_Document_array_index_nospec.patch queue-4.14/x86entry64_Remove_the_SYSCALL64_fast_path.patch queue-4.14/x86retpoline_Remove_the_esprsp_thunk.patch queue-4.14/x86bugs_Drop_one_mitigation_from_dmesg.patch queue-4.14/x86cpufeatures_Add_AMD_feature_bits_for_Speculation_Control.patch queue-4.14/scripts-faddr2line-fix-cross_compile-unset-error.patch queue-4.14/KVMSVM_Allow_direct_access_to_MSR_IA32_SPEC_CTRL.patch queue-4.14/x86asm_Move_status_from_thread_struct_to_thread_info.patch queue-4.14/KVMx86_Add_IBPB_support.patch queue-4.14/x86_Implement_array_index_mask_nospec.patch queue-4.14/KVMVMX_Emulate_MSR_IA32_ARCH_CAPABILITIES.patch queue-4.14/nl80211_Sanitize_array_index_in_parse_txq_params.patch queue-4.14/moduleretpoline_Warn_about_missing_retpoline_in_module.patch queue-4.14/x86speculation_Add_basic_IBPB_(Indirect_Branch_Prediction_Barrier)_support.patch queue-4.14/x86speculation_Simplify_indirect_branch_prediction_barrier().patch queue-4.14/x86nospec_Fix_header_guards_names.patch queue-4.14/KVM_x86_Make_indirect_calls_in_emulator_speculation_safe.patch queue-4.14/x86uaccess_Use___uaccess_begin_nospec()_and_uaccess_try_nospec.patch queue-4.14/x86entry64_Push_extra_regs_right_away.patch queue-4.14/x86usercopy_Replace_open_coded_stacclac_with___uaccess_begin_end.patch queue-4.14/vfs_fdtable_Prevent_bounds-check_bypass_via_speculative_execution.patch queue-4.14/x86retpoline_Simplify_vmexit_fill_RSB().patch queue-4.14/objtool_Warn_on_stripped_section_symbol.patch queue-4.14/x86spectre_Report_get_user_mitigation_for_spectre_v1.patch queue-4.14/x86cpufeatures_Clean_up_Spectre_v2_related_CPUID_flags.patch queue-4.14/x86syscall_Sanitize_syscall_table_de-references_under_speculation.patch queue-4.14/objtool_Improve_retpoline_alternative_handling.patch