From a35780005eb256eb5ec83ffcc802967295887a45 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Mon, 6 Jul 2009 16:10:23 +0800 Subject: 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 Signed-off-by: Li Zefan Acked-by: Frederic Weisbecker Cc: Steven Rostedt LKML-Reference: <4A51B16F.6010608@cn.fujitsu.com> Signed-off-by: Ingo Molnar --- kernel/trace/trace_workqueue.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-) (limited to 'kernel/trace/trace_workqueue.c') diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c index 97fcea4acce..40cafb07dff 100644 --- a/kernel/trace/trace_workqueue.c +++ b/kernel/trace/trace_workqueue.c @@ -9,6 +9,7 @@ #include #include #include +#include #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 @@ struct workqueue_global_stats { 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 @@ static void probe_workqueue_creation(struct task_struct *wq_thread, int cpu) 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 @@ static void probe_workqueue_destruction(struct task_struct *wq_thread) 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 @@ static struct cpu_workqueue_stats *workqueue_stat_start_cpu(int cpu) 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_start(struct tracer_stat *trace) 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 @@ static void *workqueue_stat_next(void *prev, int idx) 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 @@ static int workqueue_stat_show(struct seq_file *s, void *p) 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 @@ struct tracer_stat workqueue_stats __read_mostly = { .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 }; -- cgit v1.2.3-70-g09d2