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

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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: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Oleg Nesterov 2013-07-26 19:25:36 +02:00 committed by Steven Rostedt
parent 1a11126bcb
commit bc6f6b08de
1 changed files with 20 additions and 10 deletions
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30
kernel/trace/trace_events.c
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@ -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;
@ -722,8 +729,11 @@ 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);
ret = ftrace_event_enable_disable(file, val);
file = event_file_data(filp);
if (likely(file))
ret = ftrace_event_enable_disable(file, val);
mutex_unlock(&event_mutex);
break;