Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759119Ab3GZRbI (ORCPT ); Fri, 26 Jul 2013 13:31:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5461 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758252Ab3GZRbD (ORCPT ); Fri, 26 Jul 2013 13:31:03 -0400 Date: Fri, 26 Jul 2013 19:25:40 +0200 From: Oleg Nesterov To: Steven Rostedt , Masami Hiramatsu Cc: Alexander Z Lam , Arnaldo Carvalho de Melo , David Sharp , Frederic Weisbecker , Greg Kroah-Hartman , Ingo Molnar , Peter Zijlstra , Srikar Dronamraju , Vaibhav Nagarnaik , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org Subject: [PATCH v2 3/6] tracing: Change event_filter_read/write to verify i_private != NULL Message-ID: <20130726172540.GA3619@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130726172513.GA3586@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4286 Lines: 159 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. Signed-off-by: Oleg Nesterov --- 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; } -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/