tracing/workqueues: Add refcnt to struct cpu_workqueue_stats
The stat entries can be freed when the stat file is being read.
The worse is, the ptr can be freed immediately after it's returned
from workqueue_stat_start/next().
Add a refcnt to struct cpu_workqueue_stats to avoid use-after-free.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A51B16F.6010608@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
index 97fcea4..40cafb0 100644
--- a/kernel/trace/trace_workqueue.c
+++ b/kernel/trace/trace_workqueue.c
@@ -9,6 +9,7 @@
#include <trace/events/workqueue.h>
#include <linux/list.h>
#include <linux/percpu.h>
+#include <linux/kref.h>
#include "trace_stat.h"
#include "trace.h"
@@ -16,6 +17,7 @@
/* A cpu workqueue thread */
struct cpu_workqueue_stats {
struct list_head list;
+ struct kref kref;
int cpu;
pid_t pid;
/* Can be inserted from interrupt or user context, need to be atomic */
@@ -39,6 +41,11 @@
static DEFINE_PER_CPU(struct workqueue_global_stats, all_workqueue_stat);
#define workqueue_cpu_stat(cpu) (&per_cpu(all_workqueue_stat, cpu))
+static void cpu_workqueue_stat_free(struct kref *kref)
+{
+ kfree(container_of(kref, struct cpu_workqueue_stats, kref));
+}
+
/* Insertion of a work */
static void
probe_workqueue_insertion(struct task_struct *wq_thread,
@@ -96,8 +103,8 @@
return;
}
INIT_LIST_HEAD(&cws->list);
+ kref_init(&cws->kref);
cws->cpu = cpu;
-
cws->pid = wq_thread->pid;
spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
@@ -118,7 +125,7 @@
list) {
if (node->pid == wq_thread->pid) {
list_del(&node->list);
- kfree(node);
+ kref_put(&node->kref, cpu_workqueue_stat_free);
goto found;
}
}
@@ -137,9 +144,11 @@
spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
- if (!list_empty(&workqueue_cpu_stat(cpu)->list))
+ if (!list_empty(&workqueue_cpu_stat(cpu)->list)) {
ret = list_entry(workqueue_cpu_stat(cpu)->list.next,
struct cpu_workqueue_stats, list);
+ kref_get(&ret->kref);
+ }
spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
@@ -162,9 +171,9 @@
static void *workqueue_stat_next(void *prev, int idx)
{
struct cpu_workqueue_stats *prev_cws = prev;
+ struct cpu_workqueue_stats *ret;
int cpu = prev_cws->cpu;
unsigned long flags;
- void *ret = NULL;
spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
if (list_is_last(&prev_cws->list, &workqueue_cpu_stat(cpu)->list)) {
@@ -175,11 +184,14 @@
return NULL;
} while (!(ret = workqueue_stat_start_cpu(cpu)));
return ret;
+ } else {
+ ret = list_entry(prev_cws->list.next,
+ struct cpu_workqueue_stats, list);
+ kref_get(&ret->kref);
}
spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
- return list_entry(prev_cws->list.next, struct cpu_workqueue_stats,
- list);
+ return ret;
}
static int workqueue_stat_show(struct seq_file *s, void *p)
@@ -203,6 +215,13 @@
return 0;
}
+static void workqueue_stat_release(void *stat)
+{
+ struct cpu_workqueue_stats *node = stat;
+
+ kref_put(&node->kref, cpu_workqueue_stat_free);
+}
+
static int workqueue_stat_headers(struct seq_file *s)
{
seq_printf(s, "# CPU INSERTED EXECUTED NAME\n");
@@ -215,6 +234,7 @@
.stat_start = workqueue_stat_start,
.stat_next = workqueue_stat_next,
.stat_show = workqueue_stat_show,
+ .stat_release = workqueue_stat_release,
.stat_headers = workqueue_stat_headers
};