linux-kernel - Re: [PATCH 2/2] PM: Fix Oops from NULL pointer dereference in wakeup_source

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Date:	Wed, 20 Nov 2013 21:26:56 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	shuah.kh@...sung.com
Cc:	len.brown@...el.com, pavel@....cz, rjw@...ysocki.net,
	gregkh@...uxfoundation.org, anton@...msg.org, dwmw2@...radead.org,
	fweisbec@...il.com, mingo@...hat.com, keun-o.park@...driver.com,
	paul.gortmaker@...driver.com, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, shuahkhan@...il.com,
	stable@...r.kernel.org
Subject: Re: [PATCH 2/2] PM: Fix Oops from NULL pointer dereference in
 wakeup_source_activate

On Wed, 20 Nov 2013 19:01:22 -0700
Shuah Khan <shuah.kh@...sung.com> wrote:

> On 11/20/2013 06:40 PM, Shuah Khan wrote:

> > ---
> >   include/trace/events/power.h | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/trace/events/power.h b/include/trace/events/power.h
> > index cda100d..5ba545a 100644
> > --- a/include/trace/events/power.h
> > +++ b/include/trace/events/power.h
> > @@ -110,12 +110,14 @@ DECLARE_EVENT_CLASS(wakeup_source,
> >   	TP_ARGS(name, state),
> >
> >   	TP_STRUCT__entry(
> > -		__string(       name,           name            )
> > +		__string(name,  name ? name : "(no name)")
> >   		__field(        u64,            state           )
> >   	),
> >
> >   	TP_fast_assign(
> > -		__assign_str(name, name);
> > +		const char *tname = name ? name : "(no name)";
> > +
> > +		__assign_str(name, tname);
> >   		__entry->state = state;
> >   	),
> >
> >
> 
> Adding tracing maintainers.

Thanks!

This is one solution, but what about just making the tracing facility a
bit more robust for everyone. Following what glibc printf() does when
it is passed a NULL, does this patch fix it too?

-- Steve

(haven't even compile tested this)

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 52594b2..bdac88c 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -372,7 +372,8 @@ ftrace_define_fields_##call(struct ftrace_event_call *event_call)	\
 	__data_size += (len) * sizeof(type);
 
 #undef __string
-#define __string(item, src) __dynamic_array(char, item, strlen(src) + 1)
+#define __string(item, src) __dynamic_array(char, item,			\
+				    strlen((src) ? (src) : "(null)") + 1)
 
 #undef DECLARE_EVENT_CLASS
 #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)	\
@@ -501,7 +502,7 @@ static inline notrace int ftrace_get_offsets_##call(			\
 
 #undef __assign_str
 #define __assign_str(dst, src)						\
-	strcpy(__get_str(dst), src);
+	strcpy(__get_str(dst), (src) ? (src) : "(null)");
 
 #undef TP_fast_assign
 #define TP_fast_assign(args...) args

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