tracing: Check for allocation failure in __tracing_open()

Clean up and return -ENOMEM on if the kzalloc() fails.

This also prevents a potential crash, as the pointer that failed to
allocate would be later used.

Link: http://lkml.kernel.org/r/20120711063507.GF11812@elgon.mountain

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -2390,6 +2390,9 @@ __tracing_open(struct inode *inode, struct file *file)
 
 	iter->buffer_iter = kzalloc(sizeof(*iter->buffer_iter) * num_possible_cpus(),
 				    GFP_KERNEL);
+	if (!iter->buffer_iter)
+		goto release;
+
 	/*
 	 * We make a copy of the current tracer to avoid concurrent
 	 * changes on it while we are reading.
@@ -2451,6 +2454,7 @@ __tracing_open(struct inode *inode, struct file *file)
 	mutex_unlock(&trace_types_lock);
 	kfree(iter->trace);
 	kfree(iter->buffer_iter);
+release:
 	seq_release_private(inode, file);
 	return ERR_PTR(-ENOMEM);
 }