This is a note to let you know that I've just added the patch titled x86/speculation: Add prctl() control for indirect branch speculation to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86speculation_Add_prctl()_control_for_indirect_branch_speculation.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@xxxxxxxxxxxxxxx> know about it. Subject: x86/speculation: Add prctl() control for indirect branch speculation From: Thomas Gleixner tglx@xxxxxxxxxxxxx Date: Sun Nov 25 19:33:53 2018 +0100 From: Thomas Gleixner tglx@xxxxxxxxxxxxx commit 9137bb27e60e554dab694eafa4cca241fa3a694f upstream Add the PR_SPEC_INDIRECT_BRANCH option for the PR_GET_SPECULATION_CTRL and PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of indirect branch speculation via STIBP and IBPB. Invocations: Check indirect branch speculation status with - prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0); Enable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0); Disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0); Force disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0); See Documentation/userspace-api/spec_ctrl.rst. Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Jiri Kosina <jkosina@xxxxxxx> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: David Woodhouse <dwmw@xxxxxxxxxxxx> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: Casey Schaufler <casey.schaufler@xxxxxxxxx> Cc: Asit Mallick <asit.k.mallick@xxxxxxxxx> Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx> Cc: Jon Masters <jcm@xxxxxxxxxx> Cc: Waiman Long <longman9394@xxxxxxxxx> Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Dave Stewart <david.c.stewart@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20181125185005.866780996@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- Documentation/userspace-api/spec_ctrl.rst | 9 ++++ arch/x86/include/asm/nospec-branch.h | 1 arch/x86/kernel/cpu/bugs.c | 67 ++++++++++++++++++++++++++++++ arch/x86/kernel/process.c | 5 ++ include/linux/sched.h | 9 ++++ include/uapi/linux/prctl.h | 1 6 files changed, 92 insertions(+) --- a/Documentation/userspace-api/spec_ctrl.rst +++ b/Documentation/userspace-api/spec_ctrl.rst @@ -92,3 +92,12 @@ Speculation misfeature controls * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_ENABLE, 0, 0); * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_DISABLE, 0, 0); * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_FORCE_DISABLE, 0, 0); + +- PR_SPEC_INDIR_BRANCH: Indirect Branch Speculation in User Processes + (Mitigate Spectre V2 style attacks against user processes) + + Invocations: + * prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0); + * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0); + * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0); + * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0); --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -232,6 +232,7 @@ enum spectre_v2_mitigation { enum spectre_v2_user_mitigation { SPECTRE_V2_USER_NONE, SPECTRE_V2_USER_STRICT, + SPECTRE_V2_USER_PRCTL, }; /* The Speculative Store Bypass disable variants */ --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -563,6 +563,8 @@ void arch_smt_update(void) case SPECTRE_V2_USER_STRICT: update_stibp_strict(); break; + case SPECTRE_V2_USER_PRCTL: + break; } mutex_unlock(&spec_ctrl_mutex); @@ -749,12 +751,50 @@ static int ssb_prctl_set(struct task_str return 0; } +static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) +{ + switch (ctrl) { + case PR_SPEC_ENABLE: + if (spectre_v2_user == SPECTRE_V2_USER_NONE) + return 0; + /* + * Indirect branch speculation is always disabled in strict + * mode. + */ + if (spectre_v2_user == SPECTRE_V2_USER_STRICT) + return -EPERM; + task_clear_spec_ib_disable(task); + task_update_spec_tif(task); + break; + case PR_SPEC_DISABLE: + case PR_SPEC_FORCE_DISABLE: + /* + * Indirect branch speculation is always allowed when + * mitigation is force disabled. + */ + if (spectre_v2_user == SPECTRE_V2_USER_NONE) + return -EPERM; + if (spectre_v2_user == SPECTRE_V2_USER_STRICT) + return 0; + task_set_spec_ib_disable(task); + if (ctrl == PR_SPEC_FORCE_DISABLE) + task_set_spec_ib_force_disable(task); + task_update_spec_tif(task); + break; + default: + return -ERANGE; + } + return 0; +} + int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, unsigned long ctrl) { switch (which) { case PR_SPEC_STORE_BYPASS: return ssb_prctl_set(task, ctrl); + case PR_SPEC_INDIRECT_BRANCH: + return ib_prctl_set(task, ctrl); default: return -ENODEV; } @@ -787,11 +827,34 @@ static int ssb_prctl_get(struct task_str } } +static int ib_prctl_get(struct task_struct *task) +{ + if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) + return PR_SPEC_NOT_AFFECTED; + + switch (spectre_v2_user) { + case SPECTRE_V2_USER_NONE: + return PR_SPEC_ENABLE; + case SPECTRE_V2_USER_PRCTL: + if (task_spec_ib_force_disable(task)) + return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; + if (task_spec_ib_disable(task)) + return PR_SPEC_PRCTL | PR_SPEC_DISABLE; + return PR_SPEC_PRCTL | PR_SPEC_ENABLE; + case SPECTRE_V2_USER_STRICT: + return PR_SPEC_DISABLE; + default: + return PR_SPEC_NOT_AFFECTED; + } +} + int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) { switch (which) { case PR_SPEC_STORE_BYPASS: return ssb_prctl_get(task); + case PR_SPEC_INDIRECT_BRANCH: + return ib_prctl_get(task); default: return -ENODEV; } @@ -971,6 +1034,8 @@ static char *stibp_state(void) return ", STIBP: disabled"; case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; + case SPECTRE_V2_USER_PRCTL: + return ""; } return ""; } @@ -983,6 +1048,8 @@ static char *ibpb_state(void) return ", IBPB: disabled"; case SPECTRE_V2_USER_STRICT: return ", IBPB: always-on"; + case SPECTRE_V2_USER_PRCTL: + return ""; } } return ""; --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -453,6 +453,11 @@ static unsigned long speculation_ctrl_up set_tsk_thread_flag(tsk, TIF_SSBD); else clear_tsk_thread_flag(tsk, TIF_SSBD); + + if (task_spec_ib_disable(tsk)) + set_tsk_thread_flag(tsk, TIF_SPEC_IB); + else + clear_tsk_thread_flag(tsk, TIF_SPEC_IB); } /* Return the updated threadinfo flags*/ return task_thread_info(tsk)->flags; --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1405,6 +1405,8 @@ static inline bool is_percpu_thread(void #define PFA_SPREAD_SLAB 2 /* Spread some slab caches over cpuset */ #define PFA_SPEC_SSB_DISABLE 3 /* Speculative Store Bypass disabled */ #define PFA_SPEC_SSB_FORCE_DISABLE 4 /* Speculative Store Bypass force disabled*/ +#define PFA_SPEC_IB_DISABLE 5 /* Indirect branch speculation restricted */ +#define PFA_SPEC_IB_FORCE_DISABLE 6 /* Indirect branch speculation permanently restricted */ #define TASK_PFA_TEST(name, func) \ static inline bool task_##func(struct task_struct *p) \ @@ -1436,6 +1438,13 @@ TASK_PFA_CLEAR(SPEC_SSB_DISABLE, spec_ss TASK_PFA_TEST(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable) TASK_PFA_SET(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable) +TASK_PFA_TEST(SPEC_IB_DISABLE, spec_ib_disable) +TASK_PFA_SET(SPEC_IB_DISABLE, spec_ib_disable) +TASK_PFA_CLEAR(SPEC_IB_DISABLE, spec_ib_disable) + +TASK_PFA_TEST(SPEC_IB_FORCE_DISABLE, spec_ib_force_disable) +TASK_PFA_SET(SPEC_IB_FORCE_DISABLE, spec_ib_force_disable) + static inline void current_restore_flags(unsigned long orig_flags, unsigned long flags) { --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -203,6 +203,7 @@ struct prctl_mm_map { #define PR_SET_SPECULATION_CTRL 53 /* Speculation control variants */ # define PR_SPEC_STORE_BYPASS 0 +# define PR_SPEC_INDIRECT_BRANCH 1 /* Return and control values for PR_SET/GET_SPECULATION_CTRL */ # define PR_SPEC_NOT_AFFECTED 0 # define PR_SPEC_PRCTL (1UL << 0) Patches currently in stable-queue which might be from tglx@xxxxxxxxxxxxx are queue-4.14/x86speculation_Prepare_for_conditional_IBPB_in_switch_mm.patch queue-4.14/x86speculation_Rework_SMT_state_change.patch queue-4.14/x86bugs_Switch_the_selection_of_mitigation_from_CPU_vendor_to_CPU_features.patch queue-4.14/x86Kconfig_Select_SCHED_SMT_if_SMP_enabled.patch queue-4.14/x86speculation_Move_STIPBIBPB_string_conditionals_out_of_cpu_show_common().patch queue-4.14/x86speculation_Propagate_information_about_RSB_filling_mitigation_to_sysfs.patch queue-4.14/x86speculation_Prepare_arch_smt_update_for_PRCTL_mode.patch queue-4.14/x86speculation_Enable_cross-hyperthread_spectre_v2_STIBP_mitigation.patch queue-4.14/bpf-prevent-memory-disambiguation-attack.patch queue-4.14/x86speculation_Prevent_stale_SPEC_CTRL_msr_content.patch queue-4.14/ptrace_Remove_unused_ptrace_may_access_sched_and_MODE_IBRS.patch queue-4.14/x86speculation_Mark_string_arrays_const_correctly.patch queue-4.14/x86process_Consolidate_and_simplify_switch_to_xtra_code.patch queue-4.14/x86speculation_Apply_IBPB_more_strictly_to_avoid_cross-process_data_leak.patch queue-4.14/x86speculation_Enable_prctl_mode_for_spectre_v2_user.patch queue-4.14/x86speculation_Rename_SSBD_update_functions.patch queue-4.14/x86speculation_Add_command_line_control_for_indirect_branch_speculation.patch queue-4.14/x86l1tf_Show_actual_SMT_state.patch queue-4.14/x86speculation_Split_out_TIF_update.patch queue-4.14/schedsmt_Make_sched_smt_present_track_topology.patch queue-4.14/x86retpoline_Make_CONFIG_RETPOLINE_depend_on_compiler_support.patch queue-4.14/schedsmt_Expose_sched_smt_present_static_key.patch queue-4.14/x86speculation_Reorder_the_spec_v2_code.patch queue-4.14/x86speculation_Add_prctl()_control_for_indirect_branch_speculation.patch queue-4.14/x86bugs_Update_when_to_check_for_the_LS_CFG_SSBD_mitigation.patch queue-4.14/x86speculation_Provide_IBPB_always_command_line_options.patch queue-4.14/x86speculation_Prepare_for_per_task_indirect_branch_speculation_control.patch queue-4.14/x86speculataion_Mark_command_line_parser_data___initdata.patch queue-4.14/x86speculation_Disable_STIBP_when_enhanced_IBRS_is_in_use.patch queue-4.14/x86speculation_Reorganize_speculation_control_MSRs_update.patch queue-4.14/x86bugs_Add_AMDs_SPEC_CTRL_MSR_usage.patch queue-4.14/x86speculation_Clean_up_spectre_v2_parse_cmdline().patch queue-4.14/x86speculation_Update_the_TIF_SSBD_comment.patch queue-4.14/x86speculation_Add_seccomp_Spectre_v2_user_space_protection_mode.patch queue-4.14/x86bugs_Add_AMDs_variant_of_SSB_NO.patch queue-4.14/schedcore_Fix_cpu.max_vs._cpuhotplug_deadlock.patch queue-4.14/x86speculation_Unify_conditional_spectre_v2_print_functions.patch queue-4.14/x86speculation_Avoid___switch_to_xtra_calls.patch queue-4.14/x86speculation_Remove_unnecessary_ret_variable_in_cpu_show_common().patch queue-4.14/x86bugs_Fix_the_AMD_SSBD_usage_of_the_SPEC_CTRL_MSR.patch queue-4.14/x86retpoline_Remove_minimal_retpoline_support.patch queue-4.14/x86speculation_Add_RETPOLINE_AMD_support_to_the_inline_asm_CALL_NOSPEC_variant.patch