[PATCH v3 2/5] X86: Support LSM determination of side-channel
From: Casey Schaufler <hidden>
Date: 2018-08-21 00:04:49
Also in:
lkml, selinux
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra
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 <redacted> --- 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