From mboxrd@z Thu Jan 1 00:00:00 1970 From: casey.schaufler@intel.com (Casey Schaufler) Date: Mon, 20 Aug 2018 17:04:41 -0700 Subject: [PATCH v3 2/5] X86: Support LSM determination of side-channel In-Reply-To: <20180821000444.7004-1-casey.schaufler@intel.com> References: <20180821000444.7004-1-casey.schaufler@intel.com> Message-ID: <20180821000444.7004-3-casey.schaufler@intel.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org When switching between tasks it may be necessary to set an indirect branch prediction barrier if the tasks are potentially vulnerable to side-channel attacks. This adds a call to security_task_safe_sidechannel so that security modules can weigh in on the decision. Signed-off-by: Casey Schaufler --- arch/x86/mm/tlb.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 6eb1f34c3c85..8714d4af06aa 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include @@ -270,11 +271,14 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, * threads. It will also not flush if we switch to idle * thread and back to the same process. It will flush if we * switch to a different non-dumpable process. + * If a security module thinks that the transition + * is unsafe do the flush. */ - if (tsk && tsk->mm && - tsk->mm->context.ctx_id != last_ctx_id && - get_dumpable(tsk->mm) != SUID_DUMP_USER) - indirect_branch_prediction_barrier(); + if (tsk && tsk->mm && tsk->mm->context.ctx_id != last_ctx_id) { + if (get_dumpable(tsk->mm) != SUID_DUMP_USER || + security_task_safe_sidechannel(tsk) != 0) + indirect_branch_prediction_barrier(); + } if (IS_ENABLED(CONFIG_VMAP_STACK)) { /* -- 2.17.1