Re: [PATCH 1/1] drm/i915: fix race condition UAF in i915_perf_add_config_ioctl

[Tvrtko Ursulin]

On 29/03/2023 01:48, Umesh Nerlige Ramappa wrote:
> On Tue, Mar 28, 2023 at 02:08:47PM +0100, Tvrtko Ursulin wrote:
> > On 28/03/2023 10:36, Min Li wrote:
> > > Userspace can guess the id value and try to race oa_config object 
> > > creation
> > > with config remove, resulting in a use-after-free if we dereference the
> > > object after unlocking the metrics_lock.  For that reason, unlocking the
> > > metrics_lock must be done after we are done dereferencing the object.
> > >
> > > Signed-off-by: Min Li <lm0963hack@xxxxxxxxx>
> >
> > Fixes: f89823c21224 ("drm/i915/perf: Implement 
> > I915_PERF_ADD/REMOVE_CONFIG interface")
> > Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
> > Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
> >
> > > ---
> > >  drivers/gpu/drm/i915/i915_perf.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_perf.c 
> > > b/drivers/gpu/drm/i915/i915_perf.c
> > > index 824a34ec0b83..93748ca2c5da 100644
> > > --- a/drivers/gpu/drm/i915/i915_perf.c
> > > +++ b/drivers/gpu/drm/i915/i915_perf.c
> > > @@ -4634,13 +4634,13 @@ int i915_perf_add_config_ioctl(struct 
> > > drm_device *dev, void *data,
> > >          err = oa_config->id;
> > >          goto sysfs_err;
> > >      }
> > > -
> > > -    mutex_unlock(&perf->metrics_lock);
> > > +    id = oa_config->id;
> > >      drm_dbg(&perf->i915->drm,
> > >          "Added config %s id=%i\n", oa_config->uuid, oa_config->id);
> > > +    mutex_unlock(&perf->metrics_lock);
> > > -    return oa_config->id;
> > > +    return id;
> > >  sysfs_err:
> > >      mutex_unlock(&perf->metrics_lock);
> >
> > LGTM.
> >
> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> >
> > Umesh or Lionel could you please double check? I can merge if 
> > confirmed okay.
>
> LGTM,
>
> Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>

Pushed to drm-intel-gt-next, thanks for the fix and reviews!

Regards,

Tvrtko