linux-kernel - Re: KASAN: stack-out-of-bounds Read in __free

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Date:   Wed, 11 Apr 2018 10:47:02 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     syzbot <syzbot+dadcc936587643d7f568@...kaller.appspotmail.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: stack-out-of-bounds Read in __free_filter

On Wed, 11 Apr 2018 05:02:02 -0700
syzbot <syzbot+dadcc936587643d7f568@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot hit the following crash on upstream commit
> b284d4d5a6785f8cd07eda2646a95782373cd01e (Tue Apr 10 19:25:30 2018 +0000)
> Merge tag 'ceph-for-4.17-rc1' of git://github.com/ceph/ceph-client
> syzbot dashboard link:  
> https://syzkaller.appspot.com/bug?extid=dadcc936587643d7f568
> 
> So far this crash happened 6 times on upstream.
> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6547381214511104
> syzkaller reproducer:  
> https://syzkaller.appspot.com/x/repro.syz?id=5485642750361600
> Raw console output:  
> https://syzkaller.appspot.com/x/log.txt?id=5352489637380096
> Kernel config:  
> https://syzkaller.appspot.com/x/.config?id=-1223000601505858474
> compiler: gcc (GCC) 8.0.1 20180301 (experimental)
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+dadcc936587643d7f568@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for  
> details.
> If you forward the report, please keep this part and the footer.
>

Can you try this patch?

-- Steve

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 33b7720e2aa1..5c07ae2ac5d7 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1705,18 +1705,16 @@ static int create_filter(struct trace_event_call *call,
 			 struct event_filter **filterp)
 {
 	struct filter_parse_error *pe = NULL;
-	struct event_filter *filter = NULL;
 	int err;
 
-	err = create_filter_start(filter_string, set_str, &pe, &filter);
+	err = create_filter_start(filter_string, set_str, &pe, filterp);
 	if (err)
 		return err;
 
-	err = process_preds(call, filter_string, filter, pe);
+	err = process_preds(call, filter_string, *filterp, pe);
 	if (err && set_str)
-		append_filter_err(pe, filter);
+		append_filter_err(pe, *filterp);
 
-	*filterp = filter;
 	return err;
 }
 
@@ -1740,24 +1738,22 @@ static int create_system_filter(struct trace_subsystem_dir *dir,
 				struct trace_array *tr,
 				char *filter_str, struct event_filter **filterp)
 {
-	struct event_filter *filter = NULL;
 	struct filter_parse_error *pe = NULL;
 	int err;
 
-	err = create_filter_start(filter_str, true, &pe, &filter);
+	err = create_filter_start(filter_str, true, &pe, filterp);
 	if (!err) {
 		err = process_system_preds(dir, tr, pe, filter_str);
 		if (!err) {
 			/* System filters just show a default message */
-			kfree(filter->filter_string);
-			filter->filter_string = NULL;
+			kfree((*filterp)->filter_string);
+			(*filterp)->filter_string = NULL;
 		} else {
-			append_filter_err(pe, filter);
+			append_filter_err(pe, *filterp);
 		}
 	}
 	create_filter_finish(pe);
 
-	*filterp = filter;
 	return err;
 }
 
@@ -1765,7 +1761,7 @@ static int create_system_filter(struct trace_subsystem_dir *dir,
 int apply_event_filter(struct trace_event_file *file, char *filter_string)
 {
 	struct trace_event_call *call = file->event_call;
-	struct event_filter *filter;
+	struct event_filter *filter = NULL;
 	int err;
 
 	if (!strcmp(strstrip(filter_string), "0")) {
@@ -1818,7 +1814,7 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
 {
 	struct event_subsystem *system = dir->subsystem;
 	struct trace_array *tr = dir->tr;
-	struct event_filter *filter;
+	struct event_filter *filter = NULL;
 	int err = 0;
 
 	mutex_lock(&event_mutex);
@@ -2025,7 +2021,7 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
 			      char *filter_str)
 {
 	int err;
-	struct event_filter *filter;
+	struct event_filter *filter = NULL;
 	struct trace_event_call *call;
 
 	mutex_lock(&event_mutex);