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authorLinus Torvalds <torvalds@linux-foundation.org>2019-07-14 21:40:33 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-14 21:40:33 +0300
commit1d039859330b874d48080885eb31f4f129c246f1 (patch)
tree5988dc49e1534ec6e1fadca6c5b5231248a63b41 /kernel
parent0c85ce135456a3927f552e738f730c47ac905ac3 (diff)
parente4557c1a46b0d32746bd309e1941914b5a6912b4 (diff)
downloadlinux-1d039859330b874d48080885eb31f4f129c246f1.tar.xz
Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar: "A number of PMU driver corner case fixes, a race fix, an event grouping fix, plus a bunch of tooling fixes/updates" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (30 commits) perf/x86/intel: Fix spurious NMI on fixed counter perf/core: Fix exclusive events' grouping perf/x86/amd/uncore: Set the thread mask for F17h L3 PMCs perf/x86/amd/uncore: Do not set 'ThreadMask' and 'SliceMask' for non-L3 PMCs perf/core: Fix race between close() and fork() perf intel-pt: Fix potential NULL pointer dereference found by the smatch tool perf intel-bts: Fix potential NULL pointer dereference found by the smatch tool perf script: Assume native_arch for pipe mode perf scripts python: export-to-sqlite.py: Fix DROP VIEW power_events_view perf scripts python: export-to-postgresql.py: Fix DROP VIEW power_events_view perf hists browser: Fix potential NULL pointer dereference found by the smatch tool perf cs-etm: Fix potential NULL pointer dereference found by the smatch tool perf parse-events: Remove unused variable: error perf parse-events: Remove unused variable 'i' perf metricgroup: Add missing list_del_init() when flushing egroups list perf tools: Use list_del_init() more thorougly perf tools: Use zfree() where applicable tools lib: Adopt zalloc()/zfree() from tools/perf perf tools: Move get_current_dir_name() cond prototype out of util.h perf namespaces: Move the conditional setns() prototype to namespaces.h ...
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c83
1 files changed, 63 insertions, 20 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 785d708f8553..eea9d52b010c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2553,6 +2553,9 @@ unlock:
return ret;
}
+static bool exclusive_event_installable(struct perf_event *event,
+ struct perf_event_context *ctx);
+
/*
* Attach a performance event to a context.
*
@@ -2567,6 +2570,8 @@ perf_install_in_context(struct perf_event_context *ctx,
lockdep_assert_held(&ctx->mutex);
+ WARN_ON_ONCE(!exclusive_event_installable(event, ctx));
+
if (event->cpu != -1)
event->cpu = cpu;
@@ -4360,7 +4365,7 @@ static int exclusive_event_init(struct perf_event *event)
{
struct pmu *pmu = event->pmu;
- if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
+ if (!is_exclusive_pmu(pmu))
return 0;
/*
@@ -4391,7 +4396,7 @@ static void exclusive_event_destroy(struct perf_event *event)
{
struct pmu *pmu = event->pmu;
- if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
+ if (!is_exclusive_pmu(pmu))
return;
/* see comment in exclusive_event_init() */
@@ -4411,14 +4416,15 @@ static bool exclusive_event_match(struct perf_event *e1, struct perf_event *e2)
return false;
}
-/* Called under the same ctx::mutex as perf_install_in_context() */
static bool exclusive_event_installable(struct perf_event *event,
struct perf_event_context *ctx)
{
struct perf_event *iter_event;
struct pmu *pmu = event->pmu;
- if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
+ lockdep_assert_held(&ctx->mutex);
+
+ if (!is_exclusive_pmu(pmu))
return true;
list_for_each_entry(iter_event, &ctx->event_list, event_entry) {
@@ -4465,12 +4471,20 @@ static void _free_event(struct perf_event *event)
if (event->destroy)
event->destroy(event);
- if (event->ctx)
- put_ctx(event->ctx);
-
+ /*
+ * Must be after ->destroy(), due to uprobe_perf_close() using
+ * hw.target.
+ */
if (event->hw.target)
put_task_struct(event->hw.target);
+ /*
+ * perf_event_free_task() relies on put_ctx() being 'last', in particular
+ * all task references must be cleaned up.
+ */
+ if (event->ctx)
+ put_ctx(event->ctx);
+
exclusive_event_destroy(event);
module_put(event->pmu->module);
@@ -4650,8 +4664,17 @@ again:
mutex_unlock(&event->child_mutex);
list_for_each_entry_safe(child, tmp, &free_list, child_list) {
+ void *var = &child->ctx->refcount;
+
list_del(&child->child_list);
free_event(child);
+
+ /*
+ * Wake any perf_event_free_task() waiting for this event to be
+ * freed.
+ */
+ smp_mb(); /* pairs with wait_var_event() */
+ wake_up_var(var);
}
no_ctx:
@@ -10930,11 +10953,6 @@ SYSCALL_DEFINE5(perf_event_open,
goto err_alloc;
}
- if ((pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE) && group_leader) {
- err = -EBUSY;
- goto err_context;
- }
-
/*
* Look up the group leader (we will attach this event to it):
*/
@@ -11022,6 +11040,18 @@ SYSCALL_DEFINE5(perf_event_open,
move_group = 0;
}
}
+
+ /*
+ * Failure to create exclusive events returns -EBUSY.
+ */
+ err = -EBUSY;
+ if (!exclusive_event_installable(group_leader, ctx))
+ goto err_locked;
+
+ for_each_sibling_event(sibling, group_leader) {
+ if (!exclusive_event_installable(sibling, ctx))
+ goto err_locked;
+ }
} else {
mutex_lock(&ctx->mutex);
}
@@ -11058,9 +11088,6 @@ SYSCALL_DEFINE5(perf_event_open,
* because we need to serialize with concurrent event creation.
*/
if (!exclusive_event_installable(event, ctx)) {
- /* exclusive and group stuff are assumed mutually exclusive */
- WARN_ON_ONCE(move_group);
-
err = -EBUSY;
goto err_locked;
}
@@ -11527,11 +11554,11 @@ static void perf_free_event(struct perf_event *event,
}
/*
- * Free an unexposed, unused context as created by inheritance by
- * perf_event_init_task below, used by fork() in case of fail.
+ * Free a context as created by inheritance by perf_event_init_task() below,
+ * used by fork() in case of fail.
*
- * Not all locks are strictly required, but take them anyway to be nice and
- * help out with the lockdep assertions.
+ * Even though the task has never lived, the context and events have been
+ * exposed through the child_list, so we must take care tearing it all down.
*/
void perf_event_free_task(struct task_struct *task)
{
@@ -11561,7 +11588,23 @@ void perf_event_free_task(struct task_struct *task)
perf_free_event(event, ctx);
mutex_unlock(&ctx->mutex);
- put_ctx(ctx);
+
+ /*
+ * perf_event_release_kernel() could've stolen some of our
+ * child events and still have them on its free_list. In that
+ * case we must wait for these events to have been freed (in
+ * particular all their references to this task must've been
+ * dropped).
+ *
+ * Without this copy_process() will unconditionally free this
+ * task (irrespective of its reference count) and
+ * _free_event()'s put_task_struct(event->hw.target) will be a
+ * use-after-free.
+ *
+ * Wait for all events to drop their context reference.
+ */
+ wait_var_event(&ctx->refcount, refcount_read(&ctx->refcount) == 1);
+ put_ctx(ctx); /* must be last */
}
}