On Wed, Feb 19, 2020 at 03:41:07PM +0100, Daniel Vetter wrote: > On Wed, Feb 19, 2020 at 2:39 PM Laurent Pinchart > <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > > > > Hi Daniel, > > > > Thank you for the patch. > > > > On Wed, Feb 19, 2020 at 11:20:34AM +0100, Daniel Vetter wrote: > > > I also did a full review of all callers, and only the xen driver > > > forgot to call drm_dev_put in the failure path. Fix that up too. > > > > I'd split this patch in two then, with the Xen first coming first, and > > with an explanation in the commit message of the second patch about why > > you call drmm_add_final_kfree() in drm_dev_alloc(). Forgot to reply to this I think. Breaks biscting, so no can't split. It's just a leak, but this entire series is full of these "would break bisecting because it would introduce a subtle leak or use-after-free". Still isn't as simple as it looks unfortunately :-/ > > > > > v2: I noticed that xen has a drm_driver.release hook, and uses > > > drm_dev_alloc(). We need to remove the kfree from > > > xen_drm_drv_release(). > > > > > > bochs also has a release hook, but leaked the drm_device ever since > > > > > > commit 0a6659bdc5e8221da99eebb176fd9591435e38de > > > Author: Gerd Hoffmann <kraxel@xxxxxxxxxx> > > > Date: Tue Dec 17 18:04:46 2013 +0100 > > > > > > drm/bochs: new driver > > > > > > This patch here fixes that leak. > > > > > > Same for virtio, started leaking with > > > > > > commit b1df3a2b24a917f8853d43fe9683c0e360d2c33a > > > Author: Gerd Hoffmann <kraxel@xxxxxxxxxx> > > > Date: Tue Feb 11 14:58:04 2020 +0100 > > > > > > drm/virtio: add drm_driver.release callback. > > > > > > Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx> > > > Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx> > > > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx > > > > > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > > > Cc: Maxime Ripard <mripard@xxxxxxxxxx> > > > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> > > > Cc: David Airlie <airlied@xxxxxxxx> > > > Cc: Daniel Vetter <daniel@xxxxxxxx> > > > Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx> > > > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx > > > --- > > > drivers/gpu/drm/drm_drv.c | 3 +++ > > > drivers/gpu/drm/xen/xen_drm_front.c | 2 +- > > > 2 files changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c > > > index 3e5627d6eba6..9e62e28bbc62 100644 > > > --- a/drivers/gpu/drm/drm_drv.c > > > +++ b/drivers/gpu/drm/drm_drv.c > > > @@ -39,6 +39,7 @@ > > > #include <drm/drm_color_mgmt.h> > > > #include <drm/drm_drv.h> > > > #include <drm/drm_file.h> > > > +#include <drm/drm_managed.h> > > > #include <drm/drm_mode_object.h> > > > #include <drm/drm_print.h> > > > > > > @@ -819,6 +820,8 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver, > > > return ERR_PTR(ret); > > > } > > > > > > + drmm_add_final_kfree(dev, dev); > > > > drmm_add_final_kfree() can only be called once. Does this mean that a > > driver using drm_dev_alloc() isn't allowed to use drmm_add_final_kfree() > > to tract its own private structure ? > > There is only _one_ final kfree() for the structure containing > drm_device. Anything else you can just allocate with drmm_kzalloc, and > it will be cleaned up before. The chicken/egg doesn't just exist > around init time with drm_device, but also at cleanup time - the list > of cleanup actions is stored in drm_device, plus the logging macros > also need a drm_device. Which means we really, really, really need to > make sure that the drm_device is the very last thing that goes away. > Hence this special case. I was semi-tempted to drill through the slab > debug layer and add a check that the drm_device pointer in the > final_kfree is actually within the slab allocation block. Just to make > sure people use this correctly, and not just as a "hey here's a random > kmalloc block I want you to release, thxokbye". Because doing that > would cause a few use-after-free (or a leak). I've added those checks now. -Daniel > -Daniel > > > > > > + > > > return dev; > > > } > > > EXPORT_SYMBOL(drm_dev_alloc); > > > diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c > > > index 4be49c1aef51..d22b5da38935 100644 > > > --- a/drivers/gpu/drm/xen/xen_drm_front.c > > > +++ b/drivers/gpu/drm/xen/xen_drm_front.c > > > @@ -461,7 +461,6 @@ static void xen_drm_drv_release(struct drm_device *dev) > > > drm_mode_config_cleanup(dev); > > > > > > drm_dev_fini(dev); > > > - kfree(dev); > > > > > > if (front_info->cfg.be_alloc) > > > xenbus_switch_state(front_info->xb_dev, > > > @@ -561,6 +560,7 @@ static int xen_drm_drv_init(struct xen_drm_front_info *front_info) > > > fail_modeset: > > > drm_kms_helper_poll_fini(drm_dev); > > > drm_mode_config_cleanup(drm_dev); > > > + drm_dev_put(drm_dev); > > > fail: > > > kfree(drm_info); > > > return ret; > > > > -- > > Regards, > > > > Laurent Pinchart > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
