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Message-ID: <aN6vivjT61-MXVlt@intel.com>
Date: Thu, 2 Oct 2025 19:59:54 +0300
From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
To: Rodrigo Vivi <rodrigo.vivi@...el.com>
Cc: Alexandr Sapozhnkiov <alsp705@...il.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Tvrtko Ursulin <tursulin@...ulin.net>,
David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
lvc-project@...uxtesting.org
Subject: Re: [PATCH 5.10] gpu/i915: fix error return in mmap_offset_attach()
On Thu, Oct 02, 2025 at 06:20:54PM +0300, Ville Syrjälä wrote:
> On Thu, Oct 02, 2025 at 09:55:58AM -0400, Rodrigo Vivi wrote:
> > On Thu, Oct 02, 2025 at 11:48:26AM +0300, Alexandr Sapozhnkiov wrote:
> > > From: Alexandr Sapozhnikov <alsp705@...il.com>
> >
> > About the subject, this is not just a 5.10 kernel issue.
> > This code is the current code in our tip.
> > So this needs to target drm-tip branch, and then Cc stable
> > and perhaps a Fixes: tag.
> >
> > >
> > > In the drm_vma_node_allow function, kmalloc may
> > > return NULL, in which case the file element will not be
> > > added to the mmo->vma_node list. It would be good to
> > > not ignore this event, but at least log an error message.
> > >
> > > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> > >
> > > Signed-off-by: Alexandr Sapozhnikov <alsp705@...il.com>
> > > ---
> > > drivers/gpu/drm/i915/gem/i915_gem_mman.c | 7 +++++--
> > > 1 file changed, 5 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> > > index a2195e28b625..adaef8f09d59 100644
> > > --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> > > @@ -706,8 +706,11 @@ mmap_offset_attach(struct drm_i915_gem_object *obj,
> > > mmo = insert_mmo(obj, mmo);
> > > GEM_BUG_ON(lookup_mmo(obj, mmap_type) != mmo);
> > > out:
> > > - if (file)
> > > - drm_vma_node_allow_once(&mmo->vma_node, file);
> > > + if (file) {
> > > + err = drm_vma_node_allow_once(&mmo->vma_node, file);
> > > + if (err)
> >
> > perhaps we also need to drm_vma_offset_remove here?
> > I mean... honest question, doubt here. Is there any further clean-up needed?
>
> Yeah, mmo->vma_node has already been linked to varius places here.
> So this will lead to use-after-free in short order.
>
> With the current code if this fails then I think all that ends up
> happening is that subsequent mmap() will fail. Maybe that's just
> fine?
Hmm, or maybe it would be better to just directly return an error
here without freeing/cleaning up anything. Looks to me like that
should work fine as well, and userspace would get the error
immediately instead of later.
>
> >
> > > + goto err;
> > > + }
> > > return mmo;
> > >
> > > err:
> > > --
> > > 2.43.0
> > >
>
> --
> Ville Syrjälä
> Intel
--
Ville Syrjälä
Intel
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