[PATCH] event: Cheking for NULL before dereferencing the pointer.

[Srivardhan]

> -----Original Message-----
> From: wayland-devel [mailto:wayland-devel-
> bounces at lists.freedesktop.org] On Behalf Of Hardening
> Sent: Friday, May 09, 2014 1:08 PM
> To: wayland-devel at lists.freedesktop.org
> Subject: Re: [PATCH] event: Cheking for NULL before dereferencing the
> pointer.
> 
> Le 09/05/2014 08:43, Srivardhan Hebbar a écrit :
> > Checking for NULL before dereferencing the wl_event_source pointer so
> > as to avoid crash.
> >
> > Signed-off-by: Srivardhan Hebbar <sri.hebbar at samsung.com>
> > ---
> >   src/event-loop.c |    7 ++++++-
> >   1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/event-loop.c b/src/event-loop.c index
> > 9790cde..b62d16e 100644
> > --- a/src/event-loop.c
> > +++ b/src/event-loop.c
> > @@ -312,7 +312,12 @@ wl_event_source_check(struct wl_event_source
> *source)
> >   WL_EXPORT int
> >   wl_event_source_remove(struct wl_event_source *source)
> >   {
> > -	struct wl_event_loop *loop = source->loop;
> > +	struct wl_event_loop *loop;
> > +
> > +	if (source == NULL)
> > +		return 0;
> > +
> > +	loop = source->loop;
> >
> >   	/* We need to explicitly remove the fd, since closing the fd
> >   	 * isn't enough in case we've dup'ed the fd. */
> >
> 
> Hello Srivardhan,
> 
> do you have a case where this check is hit ? I may be wrong but having no
> loop associated with a source event is not supposed to happen. So my guess
> is that a caller of wl_event_source_remove has forgotten to nullify the
event
> source after the call.

Hi,

I was going through the code of Weston. In the main function in compositor.c
wl_event_loop_add_signal() is called to allocate the memory for
signals[](Line no: 4196. struct wl_event_source *signals[4]). The function
returns NULL if memory allocation failed. After that there is no NULL check
for 'signals'. In the end while clearing up, this function is called. So if
memory allocation failed then a NULL is passed to this function. Hence
adding code to check for the NULL.

Thank-you,
Hebbar
> 
> Regards.
> 
> --
> David FORT
> website: http://www.hardening-consulting.com/
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