Skip to content

Commit

Permalink
tracing/filters: add filter_mutex to protect filter predicates
Browse files Browse the repository at this point in the history 
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.

[ Impact: fix trace filter corruption/crashes on parallel access ]

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Tested-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: paulmck@linux.vnet.ibm.com
LKML-Reference: <1239946028.6639.13.camel@tropicana>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
  • Loading branch information
Tom Zanussi authored and Ingo Molnar committed Apr 17, 2009
1 parent 46de405 commit ac1adc5
Show file tree
Hide file tree
Showing 3 changed files with 75 additions and 23 deletions.
4 changes: 3 additions & 1 deletion kernel/trace/trace.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -757,13 +757,15 @@ 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);

Expand Down
4 changes: 2 additions & 2 deletions kernel/trace/trace_events.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -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);
Expand Down
90 changes: 70 additions & 20 deletions kernel/trace/trace_events_filter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -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;
Expand All @@ -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)
{
Expand Down Expand Up @@ -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;

Expand All @@ -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;
Expand Down Expand Up @@ -223,7 +248,7 @@ int init_preds(struct ftrace_event_call *call)
}
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;
Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -316,28 +349,46 @@ 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,
struct filter_pred *pred)
{
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;
Expand All @@ -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;
}
Expand Down

0 comments on commit ac1adc5

Please sign in to comment.