[GIT pull] perf fixes for 4.11
From: Thomas Gleixner
Date: Fri Mar 17 2017 - 15:16:29 EST
Linus,
please pull the latest perf-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf-urgent-for-linus
A set of perf related fixes:
- Fix a CR4.PCE propagation issue caused by usage of mm instead of
active_mm and therefore propagated the wrong value.
- Perf core fixes, which plug a use-after-free issue and make the event
inheritance on fork more robust.
- A tooling fix for symbol handling
Thanks,
tglx
------------------>
Andy Lutomirski (2):
x86/perf: Fix CR4.PCE propagation to use active_mm instead of mm
x86/perf: Clarify why x86_pmu_event_mapped() isn't racy
Daniel Borkmann (1):
perf symbols: Fix symbols__fixup_end heuristic for corner cases
Peter Zijlstra (4):
perf/core: Fix use-after-free in perf_release()
perf/core: Fix event inheritance on fork()
perf/core: Simplify perf_event_free_task()
perf/core: Better explain the inherit magic
arch/x86/events/core.c | 16 ++++++++++--
kernel/events/core.c | 64 ++++++++++++++++++++++++++++++++++++------------
tools/perf/util/symbol.c | 2 +-
3 files changed, 63 insertions(+), 19 deletions(-)
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 1635c0c8df23..183a972f9210 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2100,8 +2100,8 @@ static int x86_pmu_event_init(struct perf_event *event)
static void refresh_pce(void *ignored)
{
- if (current->mm)
- load_mm_cr4(current->mm);
+ if (current->active_mm)
+ load_mm_cr4(current->active_mm);
}
static void x86_pmu_event_mapped(struct perf_event *event)
@@ -2109,6 +2109,18 @@ static void x86_pmu_event_mapped(struct perf_event *event)
if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
return;
+ /*
+ * This function relies on not being called concurrently in two
+ * tasks in the same mm. Otherwise one task could observe
+ * perf_rdpmc_allowed > 1 and return all the way back to
+ * userspace with CR4.PCE clear while another task is still
+ * doing on_each_cpu_mask() to propagate CR4.PCE.
+ *
+ * For now, this can't happen because all callers hold mmap_sem
+ * for write. If this changes, we'll need a different solution.
+ */
+ lockdep_assert_held_exclusive(¤t->mm->mmap_sem);
+
if (atomic_inc_return(¤t->mm->context.perf_rdpmc_allowed) == 1)
on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1);
}
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1031bdf9f012..7298e149b732 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4254,7 +4254,7 @@ int perf_event_release_kernel(struct perf_event *event)
raw_spin_lock_irq(&ctx->lock);
/*
- * Mark this even as STATE_DEAD, there is no external reference to it
+ * Mark this event as STATE_DEAD, there is no external reference to it
* anymore.
*
* Anybody acquiring event->child_mutex after the below loop _must_
@@ -10415,21 +10415,22 @@ void perf_event_free_task(struct task_struct *task)
continue;
mutex_lock(&ctx->mutex);
-again:
- list_for_each_entry_safe(event, tmp, &ctx->pinned_groups,
- group_entry)
- perf_free_event(event, ctx);
+ raw_spin_lock_irq(&ctx->lock);
+ /*
+ * Destroy the task <-> ctx relation and mark the context dead.
+ *
+ * This is important because even though the task hasn't been
+ * exposed yet the context has been (through child_list).
+ */
+ RCU_INIT_POINTER(task->perf_event_ctxp[ctxn], NULL);
+ WRITE_ONCE(ctx->task, TASK_TOMBSTONE);
+ put_task_struct(task); /* cannot be last */
+ raw_spin_unlock_irq(&ctx->lock);
- list_for_each_entry_safe(event, tmp, &ctx->flexible_groups,
- group_entry)
+ list_for_each_entry_safe(event, tmp, &ctx->event_list, event_entry)
perf_free_event(event, ctx);
- if (!list_empty(&ctx->pinned_groups) ||
- !list_empty(&ctx->flexible_groups))
- goto again;
-
mutex_unlock(&ctx->mutex);
-
put_ctx(ctx);
}
}
@@ -10467,7 +10468,12 @@ const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
}
/*
- * inherit a event from parent task to child task:
+ * Inherit a event from parent task to child task.
+ *
+ * Returns:
+ * - valid pointer on success
+ * - NULL for orphaned events
+ * - IS_ERR() on error
*/
static struct perf_event *
inherit_event(struct perf_event *parent_event,
@@ -10561,6 +10567,16 @@ inherit_event(struct perf_event *parent_event,
return child_event;
}
+/*
+ * Inherits an event group.
+ *
+ * This will quietly suppress orphaned events; !inherit_event() is not an error.
+ * This matches with perf_event_release_kernel() removing all child events.
+ *
+ * Returns:
+ * - 0 on success
+ * - <0 on error
+ */
static int inherit_group(struct perf_event *parent_event,
struct task_struct *parent,
struct perf_event_context *parent_ctx,
@@ -10575,6 +10591,11 @@ static int inherit_group(struct perf_event *parent_event,
child, NULL, child_ctx);
if (IS_ERR(leader))
return PTR_ERR(leader);
+ /*
+ * @leader can be NULL here because of is_orphaned_event(). In this
+ * case inherit_event() will create individual events, similar to what
+ * perf_group_detach() would do anyway.
+ */
list_for_each_entry(sub, &parent_event->sibling_list, group_entry) {
child_ctr = inherit_event(sub, parent, parent_ctx,
child, leader, child_ctx);
@@ -10584,6 +10605,17 @@ static int inherit_group(struct perf_event *parent_event,
return 0;
}
+/*
+ * Creates the child task context and tries to inherit the event-group.
+ *
+ * Clears @inherited_all on !attr.inherited or error. Note that we'll leave
+ * inherited_all set when we 'fail' to inherit an orphaned event; this is
+ * consistent with perf_event_release_kernel() removing all child events.
+ *
+ * Returns:
+ * - 0 on success
+ * - <0 on error
+ */
static int
inherit_task_group(struct perf_event *event, struct task_struct *parent,
struct perf_event_context *parent_ctx,
@@ -10606,7 +10638,6 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
* First allocate and initialize a context for the
* child.
*/
-
child_ctx = alloc_perf_context(parent_ctx->pmu, child);
if (!child_ctx)
return -ENOMEM;
@@ -10668,7 +10699,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
ret = inherit_task_group(event, parent, parent_ctx,
child, ctxn, &inherited_all);
if (ret)
- break;
+ goto out_unlock;
}
/*
@@ -10684,7 +10715,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
ret = inherit_task_group(event, parent, parent_ctx,
child, ctxn, &inherited_all);
if (ret)
- break;
+ goto out_unlock;
}
raw_spin_lock_irqsave(&parent_ctx->lock, flags);
@@ -10712,6 +10743,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
}
raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
+out_unlock:
mutex_unlock(&parent_ctx->mutex);
perf_unpin_context(parent_ctx);
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 70e389bc4af7..9b4d8ba22fed 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -202,7 +202,7 @@ void symbols__fixup_end(struct rb_root *symbols)
/* Last entry */
if (curr->end == curr->start)
- curr->end = roundup(curr->start, 4096);
+ curr->end = roundup(curr->start, 4096) + 4096;
}
void __map_groups__fixup_end(struct map_groups *mg, enum map_type type)