tracing: Prevent deleting instances when they are being read

Add a ref count to the trace_array structure and prevent removal
of instances that have open descriptors.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c547ebbe36ff..3a89496dc99b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2613,6 +2613,8 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
                 tracing_iter_reset(iter, cpu);
         }
 
+        tr->ref++;
+
         mutex_unlock(&trace_types_lock);
 
         return iter;
@@ -2649,6 +2651,10 @@ static int tracing_release(struct inode *inode, struct file *file)
         tr = iter->tr;
 
         mutex_lock(&trace_types_lock);
+
+        WARN_ON(!tr->ref);
+        tr->ref--;
+
         for_each_tracing_cpu(cpu) {
                 if (iter->buffer_iter[cpu])
                         ring_buffer_read_finish(iter->buffer_iter[cpu]);
@@ -4460,6 +4466,10 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
         if (!info)
                 return -ENOMEM;
 
+        mutex_lock(&trace_types_lock);
+
+        tr->ref++;
+
         info->iter.tr           = tr;
         info->iter.cpu_file     = tc->cpu;
         info->iter.trace        = tr->current_trace;
@@ -4470,6 +4480,8 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
 
         filp->private_data = info;
 
+        mutex_unlock(&trace_types_lock);
+
         return nonseekable_open(inode, filp);
 }
 
@@ -4568,10 +4580,17 @@ static int tracing_buffers_release(struct inode *inode, struct file *file)
         struct ftrace_buffer_info *info = file->private_data;
         struct trace_iterator *iter = &info->iter;
 
+        mutex_lock(&trace_types_lock);
+
+        WARN_ON(!iter->tr->ref);
+        iter->tr->ref--;
+
         if (info->spare)
                 ring_buffer_free_read_page(iter->trace_buffer->buffer, info->spare);
         kfree(info);
 
+        mutex_unlock(&trace_types_lock);
+
         return 0;
 }
 
@@ -5411,6 +5430,10 @@ static int instance_delete(const char *name)
         if (!found)
                 goto out_unlock;
 
+        ret = -EBUSY;
+        if (tr->ref)
+                goto out_unlock;
+
         list_del(&tr->list);
 
         event_trace_del_tracer(tr);