Messages in this thread | | | Date | Tue, 4 Sep 2018 18:18:55 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v3 2/3] x86/speculation: apply IBPB more strictly to avoid cross-process data leak |
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On Tue, 4 Sep 2018, Jiri Kosina wrote: > if (tsk && tsk->mm && > tsk->mm->context.ctx_id != last_ctx_id && > - get_dumpable(tsk->mm) != SUID_DUMP_USER) > + ___ptrace_may_access(current, tsk, PTRACE_MODE_IBPB))
Uurgh. If X86_FEATURE_USE_IBPB is not enabled, then the whole __ptrace_may_access() overhead is just done for nothing.
> indirect_branch_prediction_barrier();
This really wants to be runtime patched:
if (static_cpu_has(X86_FEATURE_USE_IBPB)) stop_speculation(tsk, last_ctx_id);
and have an inline for that:
static inline void stop_speculation(struct task_struct *tsk, u64 last_ctx_id) { if (tsk && tsk->mm && tsk->mm->context.ctx_id != last_ctx_id && ___ptrace_may_access(current, tsk, PTRACE_MODE_IBPB)) indirect_branch_prediction_barrier(); }
which also makes the whole mess readable.
Hmm?
Thanks,
tglx
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