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Commit bc6f6b08 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
Browse files

tracing: Change event_enable/disable_read() to verify i_private != NULL 

tracing_open_generic_file() is racy, ftrace_event_file can be
already freed by rmdir or trace_remove_event_call().

Change event_enable_read() and event_disable_read() to read and
verify "file = i_private" under event_mutex.

This fixes nothing, but now we can change debugfs_remove("enable")
callers to nullify ->i_private and fix the the problem.

Link: http://lkml.kernel.org/r/20130726172536.GA3612@redhat.com



Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 1a11126b

kernel/trace/trace_events.c

+20 −10
Original line number Diff line number Diff line
@@ -684,15 +684,25 @@ static ssize_t 
event_enable_read(struct file *filp, char __user *ubuf, size_t cnt,

		  loff_t *ppos)

{

	struct ftrace_event_file *file = filp->private_data;

	struct ftrace_event_file *file;

	unsigned long flags;

	char buf[4] = "0";



	if (file->flags & FTRACE_EVENT_FL_ENABLED &&

	    !(file->flags & FTRACE_EVENT_FL_SOFT_DISABLED))

	mutex_lock(&event_mutex);

	file = event_file_data(filp);

	if (likely(file))

		flags = file->flags;

	mutex_unlock(&event_mutex);



	if (!file)

		return -ENODEV;



	if (flags & FTRACE_EVENT_FL_ENABLED &&

	    !(flags & FTRACE_EVENT_FL_SOFT_DISABLED))

		strcpy(buf, "1");



	if (file->flags & FTRACE_EVENT_FL_SOFT_DISABLED ||

	    file->flags & FTRACE_EVENT_FL_SOFT_MODE)

	if (flags & FTRACE_EVENT_FL_SOFT_DISABLED ||

	    flags & FTRACE_EVENT_FL_SOFT_MODE)

		strcat(buf, "*");



	strcat(buf, "\n");
@@ -704,13 +714,10 @@ static ssize_t 
event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,

		   loff_t *ppos)

{

	struct ftrace_event_file *file = filp->private_data;

	struct ftrace_event_file *file;

	unsigned long val;

	int ret;



	if (!file)

		return -EINVAL;



	ret = kstrtoul_from_user(ubuf, cnt, 10, &val);

	if (ret)

		return ret;
@@ -722,7 +729,10 @@ event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt, 
	switch (val) {

	case 0:

	case 1:

		ret = -ENODEV;

		mutex_lock(&event_mutex);

		file = event_file_data(filp);

		if (likely(file))

			ret = ftrace_event_enable_disable(file, val);

		mutex_unlock(&event_mutex);

		break;