linux-kernel - [PATCH 4/4] tracing/uprobes: Fix the usage of uprobe_buffer_enable() in probe_event

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Date:	Fri, 27 Jun 2014 19:01:46 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] tracing/uprobes: Fix the usage of
	uprobe_buffer_enable() in probe_event_enable()

The usage of uprobe_buffer_enable() added by dcad1a20 is very wrong,

1. uprobe_buffer_enable() and uprobe_buffer_disable() are not balanced,
   _enable() should be called only if !enabled.

2. If uprobe_buffer_enable() fails probe_event_enable() should clear
   tp.flags and free event_file_link.

3. If uprobe_register() fails it should do uprobe_buffer_disable().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/trace/trace_uprobe.c |   31 +++++++++++++++++++------------
 1 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index c4cf0ab..3c9b97e 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -911,26 +911,33 @@ probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file,
 		tu->tp.flags |= TP_FLAG_PROFILE;
 	}
 
-	ret = uprobe_buffer_enable();
-	if (ret < 0)
-		return ret;
-
 	WARN_ON(!uprobe_filter_is_empty(&tu->filter));
 
 	if (enabled)
 		return 0;
 
+	ret = uprobe_buffer_enable();
+	if (ret)
+		goto err_flags;
+
 	tu->consumer.filter = filter;
 	ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
-	if (ret) {
-		if (file) {
-			list_del(&link->list);
-			kfree(link);
-			tu->tp.flags &= ~TP_FLAG_TRACE;
-		} else
-			tu->tp.flags &= ~TP_FLAG_PROFILE;
-	}
+	if (ret)
+		goto err_buffer;
 
+	return 0;
+
+ err_buffer:
+	uprobe_buffer_disable();
+
+ err_flags:
+	if (file) {
+		list_del(&link->list);
+		kfree(link);
+		tu->tp.flags &= ~TP_FLAG_TRACE;
+	} else {
+		tu->tp.flags &= ~TP_FLAG_PROFILE;
+	}
 	return ret;
 }
 
-- 
1.5.5.1

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