> Hi
>
> On Tuesday 06 April 2010,
gregkh@suse.de wrote:
> > This is a note to let you know that we have just queued up the patch titled
> >
> > Subject: drm/radeon/kms: Fix NULL pointer dereference if memory allocation failed.
> >
> > to the 2.6.33-stable tree. Its filename is
> >
> > drm-radeon-kms-fix-null-pointer-dereference-if-memory-allocation-failed.patch
> >
> > A git repo of this tree can be found at
> >
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> >
> >
> > From fcbc451ba1948fba967198bd150ecbd10bbb7075 Mon Sep 17 00:00:00 2001
> > From: Pauli Nieminen <suokkos@gmail.com>
> > Date: Fri, 19 Mar 2010 07:44:33 +0000
> > Subject: drm/radeon/kms: Fix NULL pointer dereference if memory allocation failed.
> >
> > From: Pauli Nieminen <suokkos@gmail.com>
> >
> > commit fcbc451ba1948fba967198bd150ecbd10bbb7075 upstream.
> >
> > When there is allocation failure in radeon_cs_parser_relocs parser->nrelocs
> > is not cleaned. This causes NULL pointer defeference in radeon_cs_parser_fini
> > when clean up code is trying to loop over the relocation array and free the
> > objects.
> >
> > Fix adds a check for a possible NULL pointer in clean up code.
> [...]
>
> This patch breaks compiling kernel 2.6.33 + the current stable queue:
>
> CC [M] drivers/gpu/drm/radeon/radeon_cs.o
> /tmp/buildd/linux-sidux-2.6-2.6.33/debian/build/source_amd64_none/drivers/gpu/drm/radeon/radeon_cs.c: In function 'radeon_cs_parser_fini':
> /tmp/buildd/linux-sidux-2.6-2.6.33/debian/build/source_amd64_none/drivers/gpu/drm/radeon/radeon_cs.c:200: error: implicit declaration of function 'drm_gem_object_unreference_unlocked'
> make[6]: *** [drivers/gpu/drm/radeon/radeon_cs.o] Error 1
>
> as it depends on the introduction of drm_gem_object_unreference_unlocked()
> in:
>
> Commit: c3ae90c099bb62387507e86da7cf799850444b08
> Author: Luca Barbieri <luca@luca-barbieri.com>
> AuthorDate: Tue Feb 9 05:49:11 2010 +0000
>
> drm: introduce drm_gem_object_[handle_]unreference_unlocked
>
> This patch introduces the drm_gem_object_unreference_unlocked
> and drm_gem_object_handle_unreference_unlocked functions that
> do not require holding struct_mutex.
>
> drm_gem_object_unreference_unlocked calls the new
> ->gem_free_object_unlocked entry point if available, and
> otherwise just takes struct_mutex and just calls ->gem_free_object
>
> which in turn suggests:
>
> Commit: bc9025bdc4e2b591734cca17697093845007b63d
> Author: Luca Barbieri <luca@luca-barbieri.com>
> AuthorDate: Tue Feb 9 05:49:12 2010 +0000
>
> Use drm_gem_object_[handle_]unreference_unlocked where possible
>
> Mostly obvious simplifications.
>
> The i915 pread/pwrite ioctls, intel_overlay_put_image and
> nouveau_gem_new were incorrectly using the locked versions
> without locking: this is also fixed in this patch.
>
> which don't really look like candidates for 2.6.33-stable.
>
> > --- a/drivers/gpu/drm/radeon/radeon_cs.c
> > +++ b/drivers/gpu/drm/radeon/radeon_cs.c
> > @@ -193,11 +193,13 @@ static void radeon_cs_parser_fini(struct
> > radeon_bo_list_fence(&parser->validated, parser->ib->fence);
> > }
> > radeon_bo_list_unreserve(&parser->validated);
> > - for (i = 0; i < parser->nrelocs; i++) {
> > - if (parser->relocs[i].gobj) {
> > - mutex_lock(&parser->rdev->ddev->struct_mutex);
> > - drm_gem_object_unreference(parser->relocs[i].gobj);
> > - mutex_unlock(&parser->rdev->ddev->struct_mutex);
> > + if (parser->relocs != NULL) {
> ^ the only important part, the rest merely covers the new indentation
> level
>
> > + for (i = 0; i < parser->nrelocs; i++) {
> > + if (parser->relocs[i].gobj) {
> > + mutex_lock(&parser->rdev->ddev->struct_mutex);
> > + drm_gem_object_unreference_unlocked(parser->relocs[i].gobj);
> ^ drm_gem_object_unreference_unlocked() doesn't exist in 2.6.33, yet
> we can use drm_gem_object_unreference() instead.
>
> > + mutex_unlock(&parser->rdev->ddev->struct_mutex);
> > + }
> > }
> > }
> > kfree(parser->track);
>
> As a consequence, I'd suggest to merely backport the NULL pointer check,
> while ignoring the simplification of using the newly introduced
> drm_gem_object_unreference_unlocked() from 2.6.34:
>
> Signed-off-by: Stefan Lippers-Hollmann <s.l-h@gmx.de>
