From: Thomas Gleixner tglx@linutronix.de
commit 55a974021ec952ee460dc31ca08722158639de72 upstream.
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 tglx@linutronix.de Reviewed-by: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Jiri Kosina jkosina@suse.cz Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: David Woodhouse dwmw@amazon.co.uk Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Andi Kleen ak@linux.intel.com Cc: Dave Hansen dave.hansen@intel.com Cc: Casey Schaufler casey.schaufler@intel.com Cc: Asit Mallick asit.k.mallick@intel.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Jon Masters jcm@redhat.com Cc: Waiman Long longman9394@gmail.com Cc: Greg KH gregkh@linuxfoundation.org Cc: Dave Stewart david.c.stewart@intel.com Cc: Kees Cook keescook@chromium.org Link: https://lkml.kernel.org/r/20181125185006.144047038@linutronix.de [bwh: Backported to 4.4: adjust filename] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- Documentation/kernel-parameters.txt | 12 ++++++++++++ arch/x86/kernel/cpu/bugs.c | 34 +++++++++++++++++++++++----------- 2 files changed, 35 insertions(+), 11 deletions(-)
--- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3651,11 +3651,23 @@ bytes respectively. Such letter suffixes 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.
--- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -245,7 +245,9 @@ 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[] = { @@ -260,11 +262,13 @@ 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) @@ -310,6 +314,7 @@ spectre_v2_user_select_mitigation(enum s { 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; @@ -317,17 +322,20 @@ spectre_v2_user_select_mitigation(enum s if (!IS_ENABLED(CONFIG_SMP)) 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 @@ -339,12 +347,15 @@ spectre_v2_user_select_mitigation(enum s 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: @@ -352,7 +363,8 @@ spectre_v2_user_select_mitigation(enum s }
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 */