[PATCH 2/2] tracing: Have enable system events use the subsystem_open routine

Steven Rostedt
2011-07-06T21:21:19Z

[-- Attachment #1: 0002-tracing-Have-enable-system-events-use-the-subsystem_.patch --]
[-- Type: text/plain, Size: 3767 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

As the system name can be freed when a module is removed, the reference
to the system name that is passed to the enable routines to enable
events at a system level can point to arbitrary memory. This value is
only read, but it will just read garbage.

Change the system event enabling to use the subsystem_open routines
like the system filter routines do.

Cc: <stable@kernel.org>
Reported-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_events.c | 31 ++++++++++++++++++++++---------
1 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index ffc5b28..3e2a7c9 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -557,7 +557,7 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
loff_t *ppos)
{
const char set_to_char[4] = { '?', '0', '1', 'X' };
- const char *system = filp->private_data;
+ struct event_subsystem *system = filp->private_data;
struct ftrace_event_call *call;
char buf[2];
int set = 0;
@@ -568,7 +568,7 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
if (!call->name || !call->class || !call->class->reg)
continue;

- if (system && strcmp(call->class->system, system) != 0)
+ if (system && strcmp(call->class->system, system->name) != 0)
continue;

/*
@@ -598,7 +598,8 @@ static ssize_t
system_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
loff_t *ppos)
{
- const char *system = filp->private_data;
+ struct event_subsystem *system = filp->private_data;
+ const char *name = NULL;
unsigned long val;
char buf[64];
ssize_t ret;
@@ -622,7 +623,14 @@ system_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
if (val != 0 && val != 1)
return -EINVAL;

- ret = __ftrace_set_clr_event(NULL, system, NULL, val);
+ /*
+ * Opening of "enable" adds a ref count to system,
+ * so the name is safe to use.
+ */
+ if (system)
+ name = system->name;
+
+ ret = __ftrace_set_clr_event(NULL, name, NULL, val);
if (ret)
goto out;

@@ -862,6 +870,9 @@ static int subsystem_open(struct inode *inode, struct file *filp)
struct event_subsystem *system = NULL;
int ret;

+ if (!inode->i_private)
+ goto skip_search;
+
/* Make sure the system still exists */
mutex_lock(&event_mutex);
list_for_each_entry(system, &event_subsystems, list) {
@@ -880,8 +891,9 @@ static int subsystem_open(struct inode *inode, struct file *filp)
if (system != inode->i_private)
return -ENODEV;

+ skip_search:
ret = tracing_open_generic(inode, filp);
- if (ret < 0)
+ if (ret < 0 && system)
put_system(system);

return ret;
@@ -891,7 +903,8 @@ static int subsystem_release(struct inode *inode, struct file *file)
{
struct event_subsystem *system = inode->i_private;

- put_system(system);
+ if (system)
+ put_system(system);

return 0;
}
@@ -1041,10 +1054,11 @@ static const struct file_operations ftrace_subsystem_filter_fops = {
};

static const struct file_operations ftrace_system_enable_fops = {
- .open = tracing_open_generic,
+ .open = subsystem_open,
.read = system_enable_read,
.write = system_enable_write,
.llseek = default_llseek,
+ .release = subsystem_release,
};

static const struct file_operations ftrace_show_header_fops = {
@@ -1133,8 +1147,7 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
"'%s/filter' entry\n", name);
}

- trace_create_file("enable", 0644, system->entry,
- (void *)system->name,
+ trace_create_file("enable", 0644, system->entry, system,
&ftrace_system_enable_fops);

return system->entry;
--
1.7.5.4