[PATCH v4] drm/xe/xe_devcoredump: Check NULL before dereferencing

[Ghimiray, Himal Prasad]

> -----Original Message-----
> From: Roper, Matthew D <matthew.d.roper at intel.com>
> Sent: 25 March 2024 22:39
> To: Ghimiray, Himal Prasad <himal.prasad.ghimiray at intel.com>
> Cc: intel-xe at lists.freedesktop.org; Dixit, Ashutosh <ashutosh.dixit at intel.com>;
> Souza, Jose <jose.souza at intel.com>; Vivi, Rodrigo <rodrigo.vivi at intel.com>
> Subject: Re: [PATCH v4] drm/xe/xe_devcoredump: Check NULL before
> dereferencing
> 
> On Fri, Mar 22, 2024 at 10:54:47PM +0530, Himal Prasad Ghimiray wrote:
> > Dereference 'coredump' to access 'xe_devcoredump_snapshot' only if
> > 'coredump' is not NULL,
> 
> There wasn't actually any NULL dereference here, right?
> coredump_to_xe(coredump) is just container_of pointer math and doesn't
> dereference the pointer.  Likewise, &coredump->snapshot is also fine for NULL
> pointers.
> 
> The change looks fine as a general cleanup / future-proofing, the title just seems
> misleading since it makes it sound like there was a bug being fixed.

Hi Matt,
Yes you are right. Will modify the commit message accordingly.

BR
Himal 
> 
> 
> Matt
> 
> >
> > v2
> > - Fix commit messages.
> >
> > v3
> > - Define variables before code.(Ashutosh/Jose)
> >
> > v4
> > - Drop return check for coredump_to_xe. (Jose/Rodrigo)
> >
> > Cc: Ashutosh Dixit <ashutosh.dixit at intel.com>
> > Cc: José Roberto de Souza <jose.souza at intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
> > Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_devcoredump.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/xe/xe_devcoredump.c
> > b/drivers/gpu/drm/xe/xe_devcoredump.c
> > index 3a6263ecff01..a951043b2943 100644
> > --- a/drivers/gpu/drm/xe/xe_devcoredump.c
> > +++ b/drivers/gpu/drm/xe/xe_devcoredump.c
> > @@ -77,17 +77,19 @@ static ssize_t xe_devcoredump_read(char *buffer,
> loff_t offset,
> >  				   size_t count, void *data, size_t datalen)  {
> >  	struct xe_devcoredump *coredump = data;
> > -	struct xe_device *xe = coredump_to_xe(coredump);
> > -	struct xe_devcoredump_snapshot *ss = &coredump->snapshot;
> > +	struct xe_device *xe;
> > +	struct xe_devcoredump_snapshot *ss;
> >  	struct drm_printer p;
> >  	struct drm_print_iterator iter;
> >  	struct timespec64 ts;
> >  	int i;
> >
> > -	/* Our device is gone already... */
> > -	if (!data || !coredump_to_xe(coredump))
> > +	if (!coredump)
> >  		return -ENODEV;
> >
> > +	xe = coredump_to_xe(coredump);
> > +	ss = &coredump->snapshot;
> > +
> >  	/* Ensure delayed work is captured before continuing */
> >  	flush_work(&ss->work);
> >
> > --
> > 2.25.1
> >
> 
> --
> Matt Roper
> Graphics Software Engineer
> Linux GPU Platform Enablement
> Intel Corporation