This is a note to let you know that I've just added the patch titled
x86/speculation: Enable prctl mode for spectre_v2_user
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_Enable_prctl_mode_for_spectre_v2_user.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: Enable prctl mode for spectre_v2_user
From: Thomas Gleixner tglx@xxxxxxxxxxxxx
Date: Sun Nov 25 19:33:54 2018 +0100
From: Thomas Gleixner tglx@xxxxxxxxxxxxx
commit 7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 upstream
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 <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: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
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/20181125185005.958421388@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 7 +++-
arch/x86/kernel/cpu/bugs.c | 41 ++++++++++++++++++------
2 files changed, 38 insertions(+), 10 deletions(-)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4036,9 +4036,14 @@
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.
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -254,11 +254,13 @@ 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 {
@@ -269,6 +271,7 @@ 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)
@@ -323,12 +326,15 @@ spectre_v2_user_select_mitigation(enum s
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 */
@@ -339,6 +345,9 @@ spectre_v2_user_select_mitigation(enum s
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;
}
@@ -351,6 +360,12 @@ spectre_v2_user_select_mitigation(enum s
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 */
@@ -549,6 +564,15 @@ 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. */
@@ -564,6 +588,7 @@ void arch_smt_update(void)
update_stibp_strict();
break;
case SPECTRE_V2_USER_PRCTL:
+ update_indir_branch_cond();
break;
}
@@ -1035,7 +1060,8 @@ 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 "";
}
@@ -1043,14 +1069,11 @@ 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 "";
}
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
