(2013/07/27 2:25), Oleg Nesterov wrote: > event_filter_read/write() are racy, ftrace_event_call can be already > freed by trace_remove_event_call() callers. > > 1. Shift mutex_lock(event_mutex) from print/apply_event_filter to > the callers. > > 2. Change the callers, event_filter_read() and event_filter_write() > to read i_private under this mutex and abort if it is NULL. > > This fixes nothing, but now we can change debugfs_remove("filter") > callers to nullify ->i_private and fix the the problem.
Looks good for me. (Note: this also has some cosmetic changes) Reviewed-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com> Thanks! > > Signed-off-by: Oleg Nesterov <o...@redhat.com> > --- > kernel/trace/trace_events.c | 28 +++++++++++++++++++--------- > kernel/trace/trace_events_filter.c | 17 ++++++----------- > 2 files changed, 25 insertions(+), 20 deletions(-) > > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c > index 39cb049..b5144c4 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -978,24 +978,30 @@ static ssize_t > event_filter_read(struct file *filp, char __user *ubuf, size_t cnt, > loff_t *ppos) > { > - struct ftrace_event_call *call = filp->private_data; > + struct ftrace_event_call *call; > struct trace_seq *s; > - int r; > + int r = -ENODEV; > > if (*ppos) > return 0; > > s = kmalloc(sizeof(*s), GFP_KERNEL); > + > if (!s) > return -ENOMEM; > > trace_seq_init(s); > > - print_event_filter(call, s); > - r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len); > + mutex_lock(&event_mutex); > + call = event_file_data(filp); > + if (call) > + print_event_filter(call, s); > + mutex_unlock(&event_mutex); > > - kfree(s); > + if (call) > + r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len); > > + kfree(s); > return r; > } > > @@ -1003,9 +1009,9 @@ static ssize_t > event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt, > loff_t *ppos) > { > - struct ftrace_event_call *call = filp->private_data; > + struct ftrace_event_call *call; > char *buf; > - int err; > + int err = -ENODEV; > > if (cnt >= PAGE_SIZE) > return -EINVAL; > @@ -1020,13 +1026,17 @@ event_filter_write(struct file *filp, const char > __user *ubuf, size_t cnt, > } > buf[cnt] = '\0'; > > - err = apply_event_filter(call, buf); > + mutex_lock(&event_mutex); > + call = event_file_data(filp); > + if (call) > + err = apply_event_filter(call, buf); > + mutex_unlock(&event_mutex); > + > free_page((unsigned long) buf); > if (err < 0) > return err; > > *ppos += cnt; > - > return cnt; > } > > diff --git a/kernel/trace/trace_events_filter.c > b/kernel/trace/trace_events_filter.c > index 0c7b75a..97daa8c 100644 > --- a/kernel/trace/trace_events_filter.c > +++ b/kernel/trace/trace_events_filter.c > @@ -637,17 +637,15 @@ static void append_filter_err(struct filter_parse_state > *ps, > free_page((unsigned long) buf); > } > > +/* caller must hold event_mutex */ > void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s) > { > - struct event_filter *filter; > + struct event_filter *filter = call->filter; > > - mutex_lock(&event_mutex); > - filter = call->filter; > if (filter && filter->filter_string) > trace_seq_printf(s, "%s\n", filter->filter_string); > else > trace_seq_puts(s, "none\n"); > - mutex_unlock(&event_mutex); > } > > void print_subsystem_event_filter(struct event_subsystem *system, > @@ -1841,23 +1839,22 @@ static int create_system_filter(struct > event_subsystem *system, > return err; > } > > +/* caller must hold event_mutex */ > int apply_event_filter(struct ftrace_event_call *call, char *filter_string) > { > struct event_filter *filter; > - int err = 0; > - > - mutex_lock(&event_mutex); > + int err; > > if (!strcmp(strstrip(filter_string), "0")) { > filter_disable(call); > filter = call->filter; > if (!filter) > - goto out_unlock; > + return 0; > RCU_INIT_POINTER(call->filter, NULL); > /* Make sure the filter is not being used */ > synchronize_sched(); > __free_filter(filter); > - goto out_unlock; > + return 0; > } > > err = create_filter(call, filter_string, true, &filter); > @@ -1884,8 +1881,6 @@ int apply_event_filter(struct ftrace_event_call *call, > char *filter_string) > __free_filter(tmp); > } > } > -out_unlock: > - mutex_unlock(&event_mutex); > > return err; > } > -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/