From fa1202ef224391b6f5b26cdd44cc50495e8fab54 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 25 Nov 2018 19:33:45 +0100 Subject: x86/speculation: Add command line control for indirect branch speculation Add command line control for user space indirect branch speculation mitigations. The new option is: spectre_v2_user= The initial options are: - on: Unconditionally enabled - off: Unconditionally disabled -auto: Kernel selects mitigation (default off for now) When the spectre_v2= command line argument is either 'on' or 'off' this implies that the application to application control follows that state even if a contradicting spectre_v2_user= argument is supplied. Originally-by: Tim Chen Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185005.082720373@linutronix.de --- Documentation/admin-guide/kernel-parameters.txt | 32 +++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 19f4423e70d9..b6e5b33b9d75 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4194,9 +4194,13 @@ spectre_v2= [X86] Control mitigation of Spectre variant 2 (indirect branch speculation) vulnerability. + The default operation protects the kernel from + user space attacks. - on - unconditionally enable - off - unconditionally disable + on - unconditionally enable, implies + spectre_v2_user=on + off - unconditionally disable, implies + spectre_v2_user=off auto - kernel detects whether your CPU model is vulnerable @@ -4206,6 +4210,12 @@ CONFIG_RETPOLINE configuration option, and the compiler with which the kernel was built. + Selecting 'on' will also enable the mitigation + against user space to user space task attacks. + + Selecting 'off' will disable both the kernel and + the user space protections. + Specific mitigations can also be selected manually: retpoline - replace indirect branches @@ -4215,6 +4225,24 @@ Not specifying this option is equivalent to spectre_v2=auto. + spectre_v2_user= + [X86] Control mitigation of Spectre variant 2 + (indirect branch speculation) vulnerability between + user space tasks + + on - Unconditionally enable mitigations. Is + enforced by spectre_v2=on + + off - Unconditionally disable mitigations. Is + enforced by spectre_v2=off + + auto - Kernel selects the mitigation depending on + the available CPU features and vulnerability. + Default is off. + + Not specifying this option is equivalent to + spectre_v2_user=auto. + spec_store_bypass_disable= [HW] Control Speculative Store Bypass (SSB) Disable mitigation (Speculative Store Bypass vulnerability) -- cgit v1.2.3 From 9137bb27e60e554dab694eafa4cca241fa3a694f Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 25 Nov 2018 19:33:53 +0100 Subject: x86/speculation: Add prctl() control for indirect branch speculation 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 Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185005.866780996@linutronix.de --- 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 + tools/include/uapi/linux/prctl.h | 1 + 7 files changed, 93 insertions(+) (limited to 'Documentation') diff --git a/Documentation/userspace-api/spec_ctrl.rst b/Documentation/userspace-api/spec_ctrl.rst index 32f3d55c54b7..c4dbe6f7cdae 100644 --- 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); diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index d4d35baf0430..2adbe7b047fa 100644 --- 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 */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 9cab538e10f1..74359fff87fd 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -566,6 +566,8 @@ 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); @@ -752,12 +754,50 @@ static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl) 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; } @@ -790,11 +830,34 @@ static int ssb_prctl_get(struct task_struct *task) } } +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; } @@ -974,6 +1037,8 @@ static char *stibp_state(void) return ", STIBP: disabled"; case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; + case SPECTRE_V2_USER_PRCTL: + return ""; } return ""; } @@ -986,6 +1051,8 @@ static char *ibpb_state(void) return ", IBPB: disabled"; case SPECTRE_V2_USER_STRICT: return ", IBPB: always-on"; + case SPECTRE_V2_USER_PRCTL: + return ""; } } return ""; diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index afbe2eb4a1c6..7d31192296a8 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -450,6 +450,11 @@ static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk) 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; diff --git a/include/linux/sched.h b/include/linux/sched.h index a51c13c2b1a0..d607db5fcc6a 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1453,6 +1453,8 @@ 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) \ @@ -1484,6 +1486,13 @@ TASK_PFA_CLEAR(SPEC_SSB_DISABLE, spec_ssb_disable) 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) { diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index c0d7ea0bf5b6..b17201edfa09 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -212,6 +212,7 @@ 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) diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h index c0d7ea0bf5b6..b17201edfa09 100644 --- a/tools/include/uapi/linux/prctl.h +++ b/tools/include/uapi/linux/prctl.h @@ -212,6 +212,7 @@ 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) -- cgit v1.2.3 From 7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 25 Nov 2018 19:33:54 +0100 Subject: x86/speculation: Enable prctl mode for spectre_v2_user Now that all prerequisites are in place: - Add the prctl command line option - Default the 'auto' mode to 'prctl' - When SMT state changes, update the static key which controls the conditional STIBP evaluation on context switch. - At init update the static key which controls the conditional IBPB evaluation on context switch. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185005.958421388@linutronix.de --- Documentation/admin-guide/kernel-parameters.txt | 7 ++++- arch/x86/kernel/cpu/bugs.c | 41 +++++++++++++++++++------ 2 files changed, 38 insertions(+), 10 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b6e5b33b9d75..a9b98a4e8789 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4236,9 +4236,14 @@ off - Unconditionally disable mitigations. Is enforced by spectre_v2=off + prctl - Indirect branch speculation is enabled, + but mitigation can be enabled via prctl + per thread. The mitigation control state + is inherited on fork. + auto - Kernel selects the mitigation depending on the available CPU features and vulnerability. - Default is off. + Default is prctl. Not specifying this option is equivalent to spectre_v2_user=auto. diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 74359fff87fd..d0137d10f9a6 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -255,11 +255,13 @@ enum spectre_v2_user_cmd { SPECTRE_V2_USER_CMD_NONE, SPECTRE_V2_USER_CMD_AUTO, SPECTRE_V2_USER_CMD_FORCE, + SPECTRE_V2_USER_CMD_PRCTL, }; static const char * const spectre_v2_user_strings[] = { [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", + [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", }; static const struct { @@ -270,6 +272,7 @@ static const struct { { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, { "off", SPECTRE_V2_USER_CMD_NONE, false }, { "on", SPECTRE_V2_USER_CMD_FORCE, true }, + { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, }; static void __init spec_v2_user_print_cond(const char *reason, bool secure) @@ -324,12 +327,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) smt_possible = false; switch (spectre_v2_parse_user_cmdline(v2_cmd)) { - case SPECTRE_V2_USER_CMD_AUTO: case SPECTRE_V2_USER_CMD_NONE: goto set_mode; case SPECTRE_V2_USER_CMD_FORCE: mode = SPECTRE_V2_USER_STRICT; break; + case SPECTRE_V2_USER_CMD_AUTO: + case SPECTRE_V2_USER_CMD_PRCTL: + mode = SPECTRE_V2_USER_PRCTL; + break; } /* Initialize Indirect Branch Prediction Barrier */ @@ -340,6 +346,9 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) case SPECTRE_V2_USER_STRICT: static_branch_enable(&switch_mm_always_ibpb); break; + case SPECTRE_V2_USER_PRCTL: + static_branch_enable(&switch_mm_cond_ibpb); + break; default: break; } @@ -352,6 +361,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED) return; + /* + * If SMT is not possible or STIBP is not available clear the STIPB + * mode. + */ + if (!smt_possible || !boot_cpu_has(X86_FEATURE_STIBP)) + mode = SPECTRE_V2_USER_NONE; set_mode: spectre_v2_user = mode; /* Only print the STIBP mode when SMT possible */ @@ -552,6 +567,15 @@ static void update_stibp_strict(void) on_each_cpu(update_stibp_msr, NULL, 1); } +/* Update the static key controlling the evaluation of TIF_SPEC_IB */ +static void update_indir_branch_cond(void) +{ + if (sched_smt_active()) + static_branch_enable(&switch_to_cond_stibp); + else + static_branch_disable(&switch_to_cond_stibp); +} + void arch_smt_update(void) { /* Enhanced IBRS implies STIBP. No update required. */ @@ -567,6 +591,7 @@ void arch_smt_update(void) update_stibp_strict(); break; case SPECTRE_V2_USER_PRCTL: + update_indir_branch_cond(); break; } @@ -1038,7 +1063,8 @@ static char *stibp_state(void) case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; case SPECTRE_V2_USER_PRCTL: - return ""; + if (static_key_enabled(&switch_to_cond_stibp)) + return ", STIBP: conditional"; } return ""; } @@ -1046,14 +1072,11 @@ static char *stibp_state(void) static char *ibpb_state(void) { if (boot_cpu_has(X86_FEATURE_IBPB)) { - switch (spectre_v2_user) { - case SPECTRE_V2_USER_NONE: - return ", IBPB: disabled"; - case SPECTRE_V2_USER_STRICT: + if (static_key_enabled(&switch_mm_always_ibpb)) return ", IBPB: always-on"; - case SPECTRE_V2_USER_PRCTL: - return ""; - } + if (static_key_enabled(&switch_mm_cond_ibpb)) + return ", IBPB: conditional"; + return ", IBPB: disabled"; } return ""; } -- cgit v1.2.3 From 6b3e64c237c072797a9ec918654a60e3a46488e2 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 25 Nov 2018 19:33:55 +0100 Subject: x86/speculation: Add seccomp Spectre v2 user space protection mode If 'prctl' mode of user space protection from spectre v2 is selected on the kernel command-line, STIBP and IBPB are applied on tasks which restrict their indirect branch speculation via prctl. SECCOMP enables the SSBD mitigation for sandboxed tasks already, so it makes sense to prevent spectre v2 user space to user space attacks as well. The Intel mitigation guide documents how STIPB works: Setting bit 1 (STIBP) of the IA32_SPEC_CTRL MSR on a logical processor prevents the predicted targets of indirect branches on any logical processor of that core from being controlled by software that executes (or executed previously) on another logical processor of the same core. Ergo setting STIBP protects the task itself from being attacked from a task running on a different hyper-thread and protects the tasks running on different hyper-threads from being attacked. While the document suggests that the branch predictors are shielded between the logical processors, the observed performance regressions suggest that STIBP simply disables the branch predictor more or less completely. Of course the document wording is vague, but the fact that there is also no requirement for issuing IBPB when STIBP is used points clearly in that direction. The kernel still issues IBPB even when STIBP is used until Intel clarifies the whole mechanism. IBPB is issued when the task switches out, so malicious sandbox code cannot mistrain the branch predictor for the next user space task on the same logical processor. Signed-off-by: Jiri Kosina Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185006.051663132@linutronix.de --- Documentation/admin-guide/kernel-parameters.txt | 9 ++++++++- arch/x86/include/asm/nospec-branch.h | 1 + arch/x86/kernel/cpu/bugs.c | 17 ++++++++++++++++- 3 files changed, 25 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a9b98a4e8789..f405281bb202 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4241,9 +4241,16 @@ per thread. The mitigation control state is inherited on fork. + seccomp + - Same as "prctl" above, but all seccomp + threads will enable the mitigation unless + they explicitly opt out. + auto - Kernel selects the mitigation depending on the available CPU features and vulnerability. - Default is prctl. + + Default mitigation: + If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl" Not specifying this option is equivalent to spectre_v2_user=auto. diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 2adbe7b047fa..032b6009baab 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -233,6 +233,7 @@ enum spectre_v2_user_mitigation { SPECTRE_V2_USER_NONE, SPECTRE_V2_USER_STRICT, SPECTRE_V2_USER_PRCTL, + SPECTRE_V2_USER_SECCOMP, }; /* The Speculative Store Bypass disable variants */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index d0137d10f9a6..c9e304960534 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -256,12 +256,14 @@ enum spectre_v2_user_cmd { SPECTRE_V2_USER_CMD_AUTO, SPECTRE_V2_USER_CMD_FORCE, SPECTRE_V2_USER_CMD_PRCTL, + SPECTRE_V2_USER_CMD_SECCOMP, }; static const char * const spectre_v2_user_strings[] = { [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", + [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl", }; static const struct { @@ -273,6 +275,7 @@ static const struct { { "off", SPECTRE_V2_USER_CMD_NONE, false }, { "on", SPECTRE_V2_USER_CMD_FORCE, true }, { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, + { "seccomp", SPECTRE_V2_USER_CMD_SECCOMP, false }, }; static void __init spec_v2_user_print_cond(const char *reason, bool secure) @@ -332,10 +335,16 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) case SPECTRE_V2_USER_CMD_FORCE: mode = SPECTRE_V2_USER_STRICT; break; - case SPECTRE_V2_USER_CMD_AUTO: case SPECTRE_V2_USER_CMD_PRCTL: mode = SPECTRE_V2_USER_PRCTL; break; + case SPECTRE_V2_USER_CMD_AUTO: + case SPECTRE_V2_USER_CMD_SECCOMP: + if (IS_ENABLED(CONFIG_SECCOMP)) + mode = SPECTRE_V2_USER_SECCOMP; + else + mode = SPECTRE_V2_USER_PRCTL; + break; } /* Initialize Indirect Branch Prediction Barrier */ @@ -347,6 +356,7 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) static_branch_enable(&switch_mm_always_ibpb); break; case SPECTRE_V2_USER_PRCTL: + case SPECTRE_V2_USER_SECCOMP: static_branch_enable(&switch_mm_cond_ibpb); break; default: @@ -591,6 +601,7 @@ void arch_smt_update(void) update_stibp_strict(); break; case SPECTRE_V2_USER_PRCTL: + case SPECTRE_V2_USER_SECCOMP: update_indir_branch_cond(); break; } @@ -833,6 +844,8 @@ void arch_seccomp_spec_mitigate(struct task_struct *task) { if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP) ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE); + if (spectre_v2_user == SPECTRE_V2_USER_SECCOMP) + ib_prctl_set(task, PR_SPEC_FORCE_DISABLE); } #endif @@ -864,6 +877,7 @@ static int ib_prctl_get(struct task_struct *task) case SPECTRE_V2_USER_NONE: return PR_SPEC_ENABLE; case SPECTRE_V2_USER_PRCTL: + case SPECTRE_V2_USER_SECCOMP: if (task_spec_ib_force_disable(task)) return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; if (task_spec_ib_disable(task)) @@ -1063,6 +1077,7 @@ static char *stibp_state(void) case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; case SPECTRE_V2_USER_PRCTL: + case SPECTRE_V2_USER_SECCOMP: if (static_key_enabled(&switch_to_cond_stibp)) return ", STIBP: conditional"; } -- cgit v1.2.3 From 55a974021ec952ee460dc31ca08722158639de72 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 25 Nov 2018 19:33:56 +0100 Subject: x86/speculation: Provide IBPB always command line options Provide the possibility to enable IBPB always in combination with 'prctl' and 'seccomp'. Add the extra command line options and rework the IBPB selection to evaluate the command instead of the mode selected by the STIPB switch case. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185006.144047038@linutronix.de --- Documentation/admin-guide/kernel-parameters.txt | 12 +++++++++ arch/x86/kernel/cpu/bugs.c | 34 +++++++++++++++++-------- 2 files changed, 35 insertions(+), 11 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index f405281bb202..05a252e5178d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4241,11 +4241,23 @@ per thread. The mitigation control state is inherited on fork. + prctl,ibpb + - Like "prctl" above, but only STIBP is + controlled per thread. IBPB is issued + always when switching between different user + space processes. + seccomp - Same as "prctl" above, but all seccomp threads will enable the mitigation unless they explicitly opt out. + seccomp,ibpb + - Like "seccomp" above, but only STIBP is + controlled per thread. IBPB is issued + always when switching between different + user space processes. + auto - Kernel selects the mitigation depending on the available CPU features and vulnerability. diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index c9e304960534..500278f5308e 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -256,7 +256,9 @@ enum spectre_v2_user_cmd { SPECTRE_V2_USER_CMD_AUTO, SPECTRE_V2_USER_CMD_FORCE, SPECTRE_V2_USER_CMD_PRCTL, + SPECTRE_V2_USER_CMD_PRCTL_IBPB, SPECTRE_V2_USER_CMD_SECCOMP, + SPECTRE_V2_USER_CMD_SECCOMP_IBPB, }; static const char * const spectre_v2_user_strings[] = { @@ -271,11 +273,13 @@ static const struct { enum spectre_v2_user_cmd cmd; bool secure; } v2_user_options[] __initdata = { - { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, - { "off", SPECTRE_V2_USER_CMD_NONE, false }, - { "on", SPECTRE_V2_USER_CMD_FORCE, true }, - { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, - { "seccomp", SPECTRE_V2_USER_CMD_SECCOMP, false }, + { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, + { "off", SPECTRE_V2_USER_CMD_NONE, false }, + { "on", SPECTRE_V2_USER_CMD_FORCE, true }, + { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, + { "prctl,ibpb", SPECTRE_V2_USER_CMD_PRCTL_IBPB, false }, + { "seccomp", SPECTRE_V2_USER_CMD_SECCOMP, false }, + { "seccomp,ibpb", SPECTRE_V2_USER_CMD_SECCOMP_IBPB, false }, }; static void __init spec_v2_user_print_cond(const char *reason, bool secure) @@ -321,6 +325,7 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) { enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE; bool smt_possible = IS_ENABLED(CONFIG_SMP); + enum spectre_v2_user_cmd cmd; if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP)) return; @@ -329,17 +334,20 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) cpu_smt_control == CPU_SMT_NOT_SUPPORTED) smt_possible = false; - switch (spectre_v2_parse_user_cmdline(v2_cmd)) { + cmd = spectre_v2_parse_user_cmdline(v2_cmd); + switch (cmd) { case SPECTRE_V2_USER_CMD_NONE: goto set_mode; case SPECTRE_V2_USER_CMD_FORCE: mode = SPECTRE_V2_USER_STRICT; break; case SPECTRE_V2_USER_CMD_PRCTL: + case SPECTRE_V2_USER_CMD_PRCTL_IBPB: mode = SPECTRE_V2_USER_PRCTL; break; case SPECTRE_V2_USER_CMD_AUTO: case SPECTRE_V2_USER_CMD_SECCOMP: + case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: if (IS_ENABLED(CONFIG_SECCOMP)) mode = SPECTRE_V2_USER_SECCOMP; else @@ -351,12 +359,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) if (boot_cpu_has(X86_FEATURE_IBPB)) { setup_force_cpu_cap(X86_FEATURE_USE_IBPB); - switch (mode) { - case SPECTRE_V2_USER_STRICT: + switch (cmd) { + case SPECTRE_V2_USER_CMD_FORCE: + case SPECTRE_V2_USER_CMD_PRCTL_IBPB: + case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: static_branch_enable(&switch_mm_always_ibpb); break; - case SPECTRE_V2_USER_PRCTL: - case SPECTRE_V2_USER_SECCOMP: + case SPECTRE_V2_USER_CMD_PRCTL: + case SPECTRE_V2_USER_CMD_AUTO: + case SPECTRE_V2_USER_CMD_SECCOMP: static_branch_enable(&switch_mm_cond_ibpb); break; default: @@ -364,7 +375,8 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) } pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n", - mode == SPECTRE_V2_USER_STRICT ? "always-on" : "conditional"); + static_key_enabled(&switch_mm_always_ibpb) ? + "always-on" : "conditional"); } /* If enhanced IBRS is enabled no STIPB required */ -- cgit v1.2.3