[PATCH] drm/xe/tracing: Fix a potential TP_printk UAF

[Thomas Hellström]

On Mon, 2024-12-23 at 15:44 +0000, Cavitt, Jonathan wrote:
> -----Original Message-----
> From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of
> Thomas Hellström
> Sent: Monday, December 23, 2024 5:43 AM
> To: intel-xe at lists.freedesktop.org
> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>; Sousa,
> Gustavo <gustavo.sousa at intel.com>; De Marchi, Lucas
> <lucas.demarchi at intel.com>; Radhakrishna Sripada
> <radhakrishna.sripada at intel.com>; Roper, Matthew D
> <matthew.d.roper at intel.com>; Vivi, Rodrigo <rodrigo.vivi at intel.com>;
> stable at vger.kernel.org
> Subject: [PATCH] drm/xe/tracing: Fix a potential TP_printk UAF
> > 
> > The commit
> > afd2627f727b ("tracing: Check "%s" dereference via the field and
> > not the TP_printk format")
> > exposes potential UAFs in the xe_bo_move trace event.
> > 
> > Fix those by avoiding dereferencing the
> > xe_mem_type_to_name[] array at TP_printk time.
> > 
> > Since some code refactoring has taken place, explicit backporting
> > may
> > be needed for kernels older than 6.10.
> > 
> > Fixes: e46d3f813abd ("drm/xe/trace: Extract bo, vm, vma traces")
> > Cc: Gustavo Sousa <gustavo.sousa at intel.com>
> > Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> > Cc: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
> > Cc: Matt Roper <matthew.d.roper at intel.com>
> > Cc: "Thomas Hellström" <thomas.hellstrom at linux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Cc: intel-xe at lists.freedesktop.org
> > Cc: <stable at vger.kernel.org> # v6.11+
> > Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> 
> I take it we're hitting the WARN_ONCE in ignore_event due to a
> test_safe_str failure?

Actually it's the WARN_ONCE in test_event_printk()

if (WARN_ON_ONCE(dereference_flags)) {


> I don't know about us hitting a UAF here, but this fix is exactly
> what was recommended
> in the comment immediately above the WARN_ONCE that we shouldn't be
> hitting, so
> this is probably correct if that's what we're trying to avoid.

I'll double-check to see if I can easily trigger the UAF.


> Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>

Thanks,
Thomas


> -Jonathan Cavitt
> 
> > ---
> >  drivers/gpu/drm/xe/xe_trace_bo.h | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_trace_bo.h
> > b/drivers/gpu/drm/xe/xe_trace_bo.h
> > index 1762dd30ba6d..ea50fee50c7d 100644
> > --- a/drivers/gpu/drm/xe/xe_trace_bo.h
> > +++ b/drivers/gpu/drm/xe/xe_trace_bo.h
> > @@ -60,8 +60,8 @@ TRACE_EVENT(xe_bo_move,
> >  	    TP_STRUCT__entry(
> >  		     __field(struct xe_bo *, bo)
> >  		     __field(size_t, size)
> > -		     __field(u32, new_placement)
> > -		     __field(u32, old_placement)
> > +		     __string(new_placement_name,
> > xe_mem_type_to_name[new_placement])
> > +		     __string(old_placement_name,
> > xe_mem_type_to_name[old_placement])
> >  		     __string(device_id, __dev_name_bo(bo))
> >  		     __field(bool, move_lacks_source)
> >  			),
> > @@ -69,15 +69,15 @@ TRACE_EVENT(xe_bo_move,
> >  	    TP_fast_assign(
> >  		   __entry->bo      = bo;
> >  		   __entry->size = bo->size;
> > -		   __entry->new_placement = new_placement;
> > -		   __entry->old_placement = old_placement;
> > +		   __assign_str(new_placement_name);
> > +		   __assign_str(old_placement_name);
> >  		   __assign_str(device_id);
> >  		   __entry->move_lacks_source = move_lacks_source;
> >  		   ),
> >  	    TP_printk("move_lacks_source:%s, migrate object %p
> > [size %zu] from %s to %s device_id:%s",
> >  		      __entry->move_lacks_source ? "yes" : "no",
> > __entry->bo, __entry->size,
> > -		      xe_mem_type_to_name[__entry->old_placement],
> > -		      xe_mem_type_to_name[__entry->new_placement],
> > __get_str(device_id))
> > +		      __get_str(old_placement_name),
> > +		      __get_str(new_placement_name),
> > __get_str(device_id))
> >  );
> >  
> >  DECLARE_EVENT_CLASS(xe_vma,
> > -- 
> > 2.47.1
> > 
> >