On Sat, Feb 01, 2020 at 05:02:47PM +0800, Hillf Danton wrote:
On Sat, 1 Feb 2020 09:17:57 +0300 Dan Carpenter wrote:
quoted
On Sat, Feb 01, 2020 at 12:32:09PM +0800, Hillf Danton wrote:
quoted
Release obj in error path.
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -196,10 +196,10 @@ static struct drm_gem_object *vgem_gem_c
return ERR_CAST(obj);
ret = drm_gem_handle_create(file, &obj->base, handle);
- drm_gem_object_put_unlocked(&obj->base);
- if (ret)
+ if (ret) {
+ drm_gem_object_put_unlocked(&obj->base);
return ERR_PTR(ret);
-
+ }
return &obj->base;
Oh yeah. It's weird that we never noticed the success path was broken.
It's been that way for three years and no one noticed at all. Very
strange.
Anyway, it already gets freed on error in drm_gem_handle_create() so
we should just delete the drm_gem_object_put_unlocked() here it looks
like.
Good catch, Dan :P
Would you please post a patch sometime convenient next week?
Sure. Will do.
regards,
dan carpenter
On Sat, Feb 1, 2020 at 5:26 PM Dan Carpenter [off-list ref] wrote:
On Sat, Feb 01, 2020 at 05:02:47PM +0800, Hillf Danton wrote:
quoted
On Sat, 1 Feb 2020 09:17:57 +0300 Dan Carpenter wrote:
quoted
On Sat, Feb 01, 2020 at 12:32:09PM +0800, Hillf Danton wrote:
quoted
Release obj in error path.
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -196,10 +196,10 @@ static struct drm_gem_object *vgem_gem_c
return ERR_CAST(obj);
ret = drm_gem_handle_create(file, &obj->base, handle);
- drm_gem_object_put_unlocked(&obj->base);
- if (ret)
+ if (ret) {
+ drm_gem_object_put_unlocked(&obj->base);
return ERR_PTR(ret);
-
+ }
return &obj->base;
Oh yeah. It's weird that we never noticed the success path was broken.
It's been that way for three years and no one noticed at all. Very
strange.
Anyway, it already gets freed on error in drm_gem_handle_create() so
we should just delete the drm_gem_object_put_unlocked() here it looks
like.
There's two refcounts here, one is the handle_count, and the other is
the underlying object refcount. I think the code is correct, except if
you race with a 2nd thread which destroys the object (through the
handle) while we still try to read gem_object->size in the caller of
this. So correct fix (I think at least) is to shuffle that temporary
reference on the object (not the handle) we hold while constructing it
around a bit, so there's no use-after free anymore in the case of a
race. I'm typing a patch for this.
Cheers, Daniel
quoted
Good catch, Dan :P
Would you please post a patch sometime convenient next week?
Sure. Will do.
regards,
dan carpenter
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch