| Message ID | 1386150778-9066-1-git-send-email-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Dec 04, 2013 at 09:52:58AM +0000, Chris Wilson wrote: > Whilst looking up the objects required for an execbuffer, an untimely > allocation failure in creating the vma results in the object being > unreferenced from two lists. The ownership during the lookup is meant to > be moved from the list of objects being looked to the vma, and this > double unreference upon error results in a use-after-free. > > Fixes regression from > commit 27173f1f95db5e74ceb35fe9a2f2f348ea11bac9 > Author: Ben Widawsky <ben@bwidawsk.net> > Date: Wed Aug 14 11:38:36 2013 +0200 > > drm/i915: Convert execbuf code to use vmas > > Based on the fix by Ben Widawsky. A note on why this is an improvement over my fix would have been nice. I had implemented something similar too, but found my eventual patch to be a little easier to understand. My real gripe is, I had already sent off my patch to be tested by QA - and they give me about a 2d turnaround (not including weekends), which means the soonest I could get this tested and get results is next Wed. So if there is no improvement, I'd really appreciate this as a cleanup on top of my patch. > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Ben Widawsky <ben@bwidawsk.net> > Cc: stable@vger.kernel.org > --- > drivers/gpu/drm/i915/i915_gem_execbuffer.c | 24 ++++++++++++++++-------- > 1 file changed, 16 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > index c7af37187dee..5663b873a1aa 100644 > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > @@ -94,7 +94,7 @@ eb_lookup_vmas(struct eb_vmas *eb, > struct drm_i915_private *dev_priv = vm->dev->dev_private; > struct drm_i915_gem_object *obj; > struct list_head objects; > - int i, ret = 0; > + int i, ret; > > INIT_LIST_HEAD(&objects); > spin_lock(&file->table_lock); > @@ -107,7 +107,7 @@ eb_lookup_vmas(struct eb_vmas *eb, > DRM_DEBUG("Invalid object handle %d at index %d\n", > exec[i].handle, i); > ret = -ENOENT; > - goto out; > + goto err; > } > > if (!list_empty(&obj->obj_exec_link)) { > @@ -115,7 +115,7 @@ eb_lookup_vmas(struct eb_vmas *eb, > DRM_DEBUG("Object %p [handle %d, index %d] appears more than once in object list\n", > obj, exec[i].handle, i); > ret = -EINVAL; > - goto out; > + goto err; > } > > drm_gem_object_reference(&obj->base); > @@ -124,7 +124,7 @@ eb_lookup_vmas(struct eb_vmas *eb, > spin_unlock(&file->table_lock); > > i = 0; > - list_for_each_entry(obj, &objects, obj_exec_link) { > + while (!list_empty(&objects)) { > struct i915_vma *vma; > struct i915_address_space *bind_vm = vm; > > @@ -136,6 +136,10 @@ eb_lookup_vmas(struct eb_vmas *eb, > (i == (args->buffer_count - 1)))) > bind_vm = &dev_priv->gtt.base; > > + obj = list_first_entry(&objects, > + struct drm_i915_gem_object, > + obj_exec_link); > + > /* > * NOTE: We can leak any vmas created here when something fails > * later on. But that's no issue since vma_unbind can deal with > @@ -148,10 +152,12 @@ eb_lookup_vmas(struct eb_vmas *eb, > if (IS_ERR(vma)) { > DRM_DEBUG("Failed to lookup VMA\n"); > ret = PTR_ERR(vma); > - goto out; > + goto err; > } > > + /* Transfer ownership from objects to the vma */ > list_add_tail(&vma->exec_list, &eb->vmas); > + list_del_init(&obj->obj_exec_link); > > vma->exec_entry = &exec[i]; > if (eb->and < 0) { > @@ -165,16 +171,18 @@ eb_lookup_vmas(struct eb_vmas *eb, > ++i; > } > > + return 0; > > -out: > + > +err: > while (!list_empty(&objects)) { > obj = list_first_entry(&objects, > struct drm_i915_gem_object, > obj_exec_link); > list_del_init(&obj->obj_exec_link); > - if (ret) > - drm_gem_object_unreference(&obj->base); > + drm_gem_object_unreference(&obj->base); > } > + /* objects already transfered to the vma will be reaped by eb_destroy */ > return ret; > } > > -- > 1.8.5 >
On Wed, Dec 04, 2013 at 09:23:24AM -0800, Ben Widawsky wrote: > On Wed, Dec 04, 2013 at 09:52:58AM +0000, Chris Wilson wrote: > > Whilst looking up the objects required for an execbuffer, an untimely > > allocation failure in creating the vma results in the object being > > unreferenced from two lists. The ownership during the lookup is meant to > > be moved from the list of objects being looked to the vma, and this > > double unreference upon error results in a use-after-free. > > > > Fixes regression from > > commit 27173f1f95db5e74ceb35fe9a2f2f348ea11bac9 > > Author: Ben Widawsky <ben@bwidawsk.net> > > Date: Wed Aug 14 11:38:36 2013 +0200 > > > > drm/i915: Convert execbuf code to use vmas > > > > Based on the fix by Ben Widawsky. > > A note on why this is an improvement over my fix would have been nice. I > had implemented something similar too, but found my eventual patch to be > a little easier to understand. It all lies in the transfer of ownership comment. With that expressed, it is no longer an object residing on two lists that we must untangle, but a temporary list that holds the lookups which we convert into eb_vma. It is clear then we only need to clean up the temporary list upon failure. > My real gripe is, I had already sent off my patch to be tested by QA - > and they give me about a 2d turnaround (not including weekends), which > means the soonest I could get this tested and get results is next Wed. > > So if there is no improvement, I'd really appreciate this as a cleanup > on top of my patch. Your changelog belies why not. -Chris
On Wed, Dec 04, 2013 at 05:37:14PM +0000, Chris Wilson wrote: > On Wed, Dec 04, 2013 at 09:23:24AM -0800, Ben Widawsky wrote: > > On Wed, Dec 04, 2013 at 09:52:58AM +0000, Chris Wilson wrote: > > > Whilst looking up the objects required for an execbuffer, an untimely > > > allocation failure in creating the vma results in the object being > > > unreferenced from two lists. The ownership during the lookup is meant to > > > be moved from the list of objects being looked to the vma, and this > > > double unreference upon error results in a use-after-free. > > > > > > Fixes regression from > > > commit 27173f1f95db5e74ceb35fe9a2f2f348ea11bac9 > > > Author: Ben Widawsky <ben@bwidawsk.net> > > > Date: Wed Aug 14 11:38:36 2013 +0200 > > > > > > drm/i915: Convert execbuf code to use vmas > > > > > > Based on the fix by Ben Widawsky. > > > > A note on why this is an improvement over my fix would have been nice. I > > had implemented something similar too, but found my eventual patch to be > > a little easier to understand. > > It all lies in the transfer of ownership comment. With that expressed, > it is no longer an object residing on two lists that we must untangle, > but a temporary list that holds the lookups which we convert into > eb_vma. It is clear then we only need to clean up the temporary list > upon failure. > > > My real gripe is, I had already sent off my patch to be tested by QA - > > and they give me about a 2d turnaround (not including weekends), which > > means the soonest I could get this tested and get results is next Wed. > > > > So if there is no improvement, I'd really appreciate this as a cleanup > > on top of my patch. > > Your changelog belies why not. Picked up for -fixes (with the comment bikeshed as discussd on irc), thanks for the patch. -Daniel
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c index c7af37187dee..5663b873a1aa 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -94,7 +94,7 @@ eb_lookup_vmas(struct eb_vmas *eb, struct drm_i915_private *dev_priv = vm->dev->dev_private; struct drm_i915_gem_object *obj; struct list_head objects; - int i, ret = 0; + int i, ret; INIT_LIST_HEAD(&objects); spin_lock(&file->table_lock); @@ -107,7 +107,7 @@ eb_lookup_vmas(struct eb_vmas *eb, DRM_DEBUG("Invalid object handle %d at index %d\n", exec[i].handle, i); ret = -ENOENT; - goto out; + goto err; } if (!list_empty(&obj->obj_exec_link)) { @@ -115,7 +115,7 @@ eb_lookup_vmas(struct eb_vmas *eb, DRM_DEBUG("Object %p [handle %d, index %d] appears more than once in object list\n", obj, exec[i].handle, i); ret = -EINVAL; - goto out; + goto err; } drm_gem_object_reference(&obj->base); @@ -124,7 +124,7 @@ eb_lookup_vmas(struct eb_vmas *eb, spin_unlock(&file->table_lock); i = 0; - list_for_each_entry(obj, &objects, obj_exec_link) { + while (!list_empty(&objects)) { struct i915_vma *vma; struct i915_address_space *bind_vm = vm; @@ -136,6 +136,10 @@ eb_lookup_vmas(struct eb_vmas *eb, (i == (args->buffer_count - 1)))) bind_vm = &dev_priv->gtt.base; + obj = list_first_entry(&objects, + struct drm_i915_gem_object, + obj_exec_link); + /* * NOTE: We can leak any vmas created here when something fails * later on. But that's no issue since vma_unbind can deal with @@ -148,10 +152,12 @@ eb_lookup_vmas(struct eb_vmas *eb, if (IS_ERR(vma)) { DRM_DEBUG("Failed to lookup VMA\n"); ret = PTR_ERR(vma); - goto out; + goto err; } + /* Transfer ownership from objects to the vma */ list_add_tail(&vma->exec_list, &eb->vmas); + list_del_init(&obj->obj_exec_link); vma->exec_entry = &exec[i]; if (eb->and < 0) { @@ -165,16 +171,18 @@ eb_lookup_vmas(struct eb_vmas *eb, ++i; } + return 0; -out: + +err: while (!list_empty(&objects)) { obj = list_first_entry(&objects, struct drm_i915_gem_object, obj_exec_link); list_del_init(&obj->obj_exec_link); - if (ret) - drm_gem_object_unreference(&obj->base); + drm_gem_object_unreference(&obj->base); } + /* objects already transfered to the vma will be reaped by eb_destroy */ return ret; }
Whilst looking up the objects required for an execbuffer, an untimely allocation failure in creating the vma results in the object being unreferenced from two lists. The ownership during the lookup is meant to be moved from the list of objects being looked to the vma, and this double unreference upon error results in a use-after-free. Fixes regression from commit 27173f1f95db5e74ceb35fe9a2f2f348ea11bac9 Author: Ben Widawsky <ben@bwidawsk.net> Date: Wed Aug 14 11:38:36 2013 +0200 drm/i915: Convert execbuf code to use vmas Based on the fix by Ben Widawsky. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Ben Widawsky <ben@bwidawsk.net> Cc: stable@vger.kernel.org --- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-)