[for-linus][PATCH 5/7] tracing/probe: Fix null pointer dereference

[Steven Rostedt <rostedt@goodmis.org>]

From: Xinpeng Liu <danielliu861@gmail.com>

BUG: KASAN: null-ptr-deref in trace_probe_cleanup+0x8d/0xd0
Read of size 8 at addr 0000000000000000 by task syz-executor.0/9746
trace_probe_cleanup+0x8d/0xd0
free_trace_kprobe.part.14+0x15/0x50
alloc_trace_kprobe+0x23e/0x250

Link: http://lkml.kernel.org/r/1565220563-980-1-git-send-email-danielliu861@gmail.com

Fixes: e3dc9f898ef9c ("tracing/probe: Add trace_event_call accesses APIs")
Signed-off-by: Xinpeng Liu <danielliu861@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_probe.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index dbef0d135075..fb6bfbc5bf86 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -895,7 +895,8 @@ void trace_probe_cleanup(struct trace_probe *tp)
 	for (i = 0; i < tp->nr_args; i++)
 		traceprobe_free_probe_arg(&tp->args[i]);
 
-	kfree(call->class->system);
+	if (call->class)
+		kfree(call->class->system);
 	kfree(call->name);
 	kfree(call->print_fmt);
 }
-- 
2.20.1