[PATCH v2] tracing/filters: add filter_mutex to protect filterpredicates

From: Tom Zanussi
Date: Fri Apr 17 2009 - 01:27:23 EST

This patch adds a filter_mutex to prevent the filter predicates from
being accessed concurrently by various external functions.

It's based on a previous patch by Li Zefan:
"[PATCH 7/7] tracing/filters: make filter preds RCU safe"

v2 changes:

- fixed wrong value returned in a add_subsystem_pred() failure case
noticed by Li Zefan.

Signed-off-by: Tom Zanussi <tzanussi@xxxxxxxxx>

---
kernel/trace/trace.h | 4 +-
kernel/trace/trace_events.c | 4 +-
kernel/trace/trace_events_filter.c | 90 ++++++++++++++++++++++++++++--------
3 files changed, 75 insertions(+), 23 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index eb92307..8750e83 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -759,13 +759,15 @@ struct filter_pred {
};

extern void filter_free_pred(struct filter_pred *pred);
-extern void filter_print_preds(struct filter_pred **preds, int n_preds,
+extern void filter_print_preds(struct ftrace_event_call *call,
struct trace_seq *s);
extern int filter_parse(char **pbuf, struct filter_pred *pred);
extern int filter_add_pred(struct ftrace_event_call *call,
struct filter_pred *pred);
extern void filter_disable_preds(struct ftrace_event_call *call);
extern void filter_free_subsystem_preds(struct event_subsystem *system);
+extern void filter_print_subsystem_preds(struct event_subsystem *system,
+ struct trace_seq *s);
extern int filter_add_subsystem_pred(struct event_subsystem *system,
struct filter_pred *pred);

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 8af3534..e6d6404 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -488,7 +488,7 @@ event_filter_read(struct file *filp, char __user *ubuf, size_t cnt,

trace_seq_init(s);

- filter_print_preds(call->preds, call->n_preds, s);
+ filter_print_preds(call, s);
r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len);

kfree(s);
@@ -558,7 +558,7 @@ subsystem_filter_read(struct file *filp, char __user *ubuf, size_t cnt,

trace_seq_init(s);

- filter_print_preds(system->preds, system->n_preds, s);
+ filter_print_subsystem_preds(system, s);
r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len);

kfree(s);
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index f8e5eab..e0fcfd2 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -22,10 +22,13 @@
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ctype.h>
+#include <linux/mutex.h>

#include "trace.h"
#include "trace_output.h"

+static DEFINE_MUTEX(filter_mutex);
+
static int filter_pred_64(struct filter_pred *pred, void *event)
{
u64 *addr = (u64 *)(event + pred->offset);
@@ -112,8 +115,8 @@ int filter_match_preds(struct ftrace_event_call *call, void *rec)
}
EXPORT_SYMBOL_GPL(filter_match_preds);

-void filter_print_preds(struct filter_pred **preds, int n_preds,
- struct trace_seq *s)
+static void __filter_print_preds(struct filter_pred **preds, int n_preds,
+ struct trace_seq *s)
{
char *field_name;
struct filter_pred *pred;
@@ -138,6 +141,21 @@ void filter_print_preds(struct filter_pred **preds, int n_preds,
}
}

+void filter_print_preds(struct ftrace_event_call *call, struct trace_seq *s)
+{
+ mutex_lock(&filter_mutex);
+ __filter_print_preds(call->preds, call->n_preds, s);
+ mutex_unlock(&filter_mutex);
+}
+
+void filter_print_subsystem_preds(struct event_subsystem *system,
+ struct trace_seq *s)
+{
+ mutex_lock(&filter_mutex);
+ __filter_print_preds(system->preds, system->n_preds, s);
+ mutex_unlock(&filter_mutex);
+}
+
static struct ftrace_event_field *
find_event_field(struct ftrace_event_call *call, char *name)
{
@@ -180,7 +198,7 @@ static int filter_set_pred(struct filter_pred *dest,
return 0;
}

-void filter_disable_preds(struct ftrace_event_call *call)
+static void __filter_disable_preds(struct ftrace_event_call *call)
{
int i;

@@ -190,6 +208,13 @@ void filter_disable_preds(struct ftrace_event_call *call)
call->preds[i]->fn = filter_pred_none;
}

+void filter_disable_preds(struct ftrace_event_call *call)
+{
+ mutex_lock(&filter_mutex);
+ __filter_disable_preds(call);
+ mutex_unlock(&filter_mutex);
+}
+
int init_preds(struct ftrace_event_call *call)
{
struct filter_pred *pred;
@@ -223,7 +248,7 @@ oom:
}
EXPORT_SYMBOL_GPL(init_preds);

-void filter_free_subsystem_preds(struct event_subsystem *system)
+static void __filter_free_subsystem_preds(struct event_subsystem *system)
{
struct ftrace_event_call *call;
int i;
@@ -241,18 +266,25 @@ void filter_free_subsystem_preds(struct event_subsystem *system)
continue;

if (!strcmp(call->system, system->name))
- filter_disable_preds(call);
+ __filter_disable_preds(call);
}
}

-static int __filter_add_pred(struct ftrace_event_call *call,
- struct filter_pred *pred,
- filter_pred_fn_t fn)
+void filter_free_subsystem_preds(struct event_subsystem *system)
+{
+ mutex_lock(&filter_mutex);
+ __filter_free_subsystem_preds(system);
+ mutex_unlock(&filter_mutex);
+}
+
+static int filter_add_pred_fn(struct ftrace_event_call *call,
+ struct filter_pred *pred,
+ filter_pred_fn_t fn)
{
int idx, err;

if (call->n_preds && !pred->compound)
- filter_disable_preds(call);
+ __filter_disable_preds(call);

if (call->n_preds == MAX_FILTER_PRED)
return -ENOSPC;
@@ -276,7 +308,8 @@ static int is_string_field(const char *type)
return 0;
}

-int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
+static int __filter_add_pred(struct ftrace_event_call *call,
+ struct filter_pred *pred)
{
struct ftrace_event_field *field;
filter_pred_fn_t fn;
@@ -293,7 +326,7 @@ int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
return -EINVAL;
fn = filter_pred_string;
pred->str_len = field->size;
- return __filter_add_pred(call, pred, fn);
+ return filter_add_pred_fn(call, pred, fn);
} else {
if (pred->str_len)
return -EINVAL;
@@ -316,7 +349,18 @@ int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
return -EINVAL;
}

- return __filter_add_pred(call, pred, fn);
+ return filter_add_pred_fn(call, pred, fn);
+}
+
+int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
+{
+ int err;
+
+ mutex_lock(&filter_mutex);
+ err = __filter_add_pred(call, pred);
+ mutex_unlock(&filter_mutex);
+
+ return err;
}

int filter_add_subsystem_pred(struct event_subsystem *system,
@@ -324,20 +368,27 @@ int filter_add_subsystem_pred(struct event_subsystem *system,
{
struct ftrace_event_call *call;

+ mutex_lock(&filter_mutex);
+
if (system->n_preds && !pred->compound)
- filter_free_subsystem_preds(system);
+ __filter_free_subsystem_preds(system);

if (!system->n_preds) {
system->preds = kzalloc(MAX_FILTER_PRED * sizeof(pred),
GFP_KERNEL);
- if (!system->preds)
+ if (!system->preds) {
+ mutex_unlock(&filter_mutex);
return -ENOMEM;
+ }
}

- if (system->n_preds == MAX_FILTER_PRED)
+ if (system->n_preds == MAX_FILTER_PRED) {
+ mutex_unlock(&filter_mutex);
return -ENOSPC;
+ }

system->preds[system->n_preds] = pred;
+ system->n_preds++;

list_for_each_entry(call, &ftrace_events, list) {
int err;
@@ -348,17 +399,16 @@ int filter_add_subsystem_pred(struct event_subsystem *system,
if (strcmp(call->system, system->name))
continue;

- if (!find_event_field(call, pred->field_name))
- continue;
-
- err = filter_add_pred(call, pred);
+ err = __filter_add_pred(call, pred);
if (err == -ENOMEM) {
system->preds[system->n_preds] = NULL;
+ system->n_preds--;
+ mutex_unlock(&filter_mutex);
return err;
}
}

- system->n_preds++;
+ mutex_unlock(&filter_mutex);

return 0;
}
--
1.5.6.3



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