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Message-Id: <20180817221624.10232-3-casey.schaufler@intel.com>
Date: Fri, 17 Aug 2018 15:16:21 -0700
From: Casey Schaufler <casey.schaufler@...el.com>
To: kernel-hardening@...ts.openwall.com,
linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
selinux@...ho.nsa.gov,
casey.schaufler@...el.com,
dave.hansen@...el.com,
deneen.t.dock@...el.com,
kristen@...ux.intel.com,
arjan@...ux.intel.com
Subject: [PATCH RFC v2 2/5] X86: Support LSM determination of side-channel vulnerability
From: Casey Schaufler <cschaufler@...alhost.localdomain>
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 <casey.schaufler@...el.com>
---
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 <linux/export.h>
#include <linux/cpu.h>
#include <linux/debugfs.h>
+#include <linux/security.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
@@ -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
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