| Message ID | 20210826020122.1488002-2-desmondcheongzx@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm: update locking for modesetting | expand |
On Thu, Aug 26, 2021 at 10:01:16AM +0800, Desmond Cheong Zhi Xi wrote: > drm_master_release can be called on a drm_file without a master, which > results in a null ptr dereference of file_priv->master->magic_map. The > three cases are: > > 1. Error path in drm_open_helper > drm_open(): > drm_open_helper(): > drm_master_open(): > drm_new_set_master(); <--- returns -ENOMEM, > drm_file.master not set > drm_file_free(): > drm_master_release(); <--- NULL ptr dereference > (file_priv->master->magic_map) > > 2. Error path in mock_drm_getfile > mock_drm_getfile(): > anon_inode_getfile(); <--- returns error, drm_file.master not set > drm_file_free(): > drm_master_release(); <--- NULL ptr dereference > (file_priv->master->magic_map) > > 3. In drm_client_close, as drm_client_open doesn't set up a master > > drm_file.master is set up in drm_open_helper through the call to > drm_master_open, so we mirror it with a call to drm_master_release in > drm_close_helper, and remove drm_master_release from drm_file_free to > avoid the null ptr dereference. > > Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> I guess we should also have a cc: stable on this one? I think this bug existed since pretty much forever, but maybe more prominent with the drm_client stuff added a while ago. -Daniel > --- > drivers/gpu/drm/drm_file.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c > index ed25168619fc..90b62f360da1 100644 > --- a/drivers/gpu/drm/drm_file.c > +++ b/drivers/gpu/drm/drm_file.c > @@ -282,9 +282,6 @@ void drm_file_free(struct drm_file *file) > > drm_legacy_ctxbitmap_flush(dev, file); > > - if (drm_is_primary_client(file)) > - drm_master_release(file); > - > if (dev->driver->postclose) > dev->driver->postclose(dev, file); > > @@ -305,6 +302,9 @@ static void drm_close_helper(struct file *filp) > list_del(&file_priv->lhead); > mutex_unlock(&dev->filelist_mutex); > > + if (drm_is_primary_client(file_priv)) > + drm_master_release(file_priv); > + > drm_file_free(file_priv); > } > > -- > 2.25.1 >
On 26/8/21 5:53 pm, Daniel Vetter wrote: > On Thu, Aug 26, 2021 at 10:01:16AM +0800, Desmond Cheong Zhi Xi wrote: >> drm_master_release can be called on a drm_file without a master, which >> results in a null ptr dereference of file_priv->master->magic_map. The >> three cases are: >> >> 1. Error path in drm_open_helper >> drm_open(): >> drm_open_helper(): >> drm_master_open(): >> drm_new_set_master(); <--- returns -ENOMEM, >> drm_file.master not set >> drm_file_free(): >> drm_master_release(); <--- NULL ptr dereference >> (file_priv->master->magic_map) >> >> 2. Error path in mock_drm_getfile >> mock_drm_getfile(): >> anon_inode_getfile(); <--- returns error, drm_file.master not set >> drm_file_free(): >> drm_master_release(); <--- NULL ptr dereference >> (file_priv->master->magic_map) >> >> 3. In drm_client_close, as drm_client_open doesn't set up a master >> >> drm_file.master is set up in drm_open_helper through the call to >> drm_master_open, so we mirror it with a call to drm_master_release in >> drm_close_helper, and remove drm_master_release from drm_file_free to >> avoid the null ptr dereference. >> >> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > > I guess we should also have a cc: stable on this one? I think this bug > existed since pretty much forever, but maybe more prominent with the > drm_client stuff added a while ago. > -Daniel > Thanks for the reviews, Daniel. Took a closer look. I think if we cc: stable, this fix should accompany commit 7eeaeb90a6a5 ("drm/file: Don't set master on in-kernel clients") which moves the drm_master_open out from drm_file_alloc into drm_open_helper. >> --- >> drivers/gpu/drm/drm_file.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c >> index ed25168619fc..90b62f360da1 100644 >> --- a/drivers/gpu/drm/drm_file.c >> +++ b/drivers/gpu/drm/drm_file.c >> @@ -282,9 +282,6 @@ void drm_file_free(struct drm_file *file) >> >> drm_legacy_ctxbitmap_flush(dev, file); >> >> - if (drm_is_primary_client(file)) >> - drm_master_release(file); >> - >> if (dev->driver->postclose) >> dev->driver->postclose(dev, file); >> >> @@ -305,6 +302,9 @@ static void drm_close_helper(struct file *filp) >> list_del(&file_priv->lhead); >> mutex_unlock(&dev->filelist_mutex); >> >> + if (drm_is_primary_client(file_priv)) >> + drm_master_release(file_priv); >> + >> drm_file_free(file_priv); >> } >> >> -- >> 2.25.1 >> >
On Thu, Aug 26, 2021 at 07:53:58PM +0800, Desmond Cheong Zhi Xi wrote: > On 26/8/21 5:53 pm, Daniel Vetter wrote: > > On Thu, Aug 26, 2021 at 10:01:16AM +0800, Desmond Cheong Zhi Xi wrote: > > > drm_master_release can be called on a drm_file without a master, which > > > results in a null ptr dereference of file_priv->master->magic_map. The > > > three cases are: > > > > > > 1. Error path in drm_open_helper > > > drm_open(): > > > drm_open_helper(): > > > drm_master_open(): > > > drm_new_set_master(); <--- returns -ENOMEM, > > > drm_file.master not set > > > drm_file_free(): > > > drm_master_release(); <--- NULL ptr dereference > > > (file_priv->master->magic_map) > > > > > > 2. Error path in mock_drm_getfile > > > mock_drm_getfile(): > > > anon_inode_getfile(); <--- returns error, drm_file.master not set > > > drm_file_free(): > > > drm_master_release(); <--- NULL ptr dereference > > > (file_priv->master->magic_map) > > > > > > 3. In drm_client_close, as drm_client_open doesn't set up a master > > > > > > drm_file.master is set up in drm_open_helper through the call to > > > drm_master_open, so we mirror it with a call to drm_master_release in > > > drm_close_helper, and remove drm_master_release from drm_file_free to > > > avoid the null ptr dereference. > > > > > > Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> > > > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > > > > I guess we should also have a cc: stable on this one? I think this bug > > existed since pretty much forever, but maybe more prominent with the > > drm_client stuff added a while ago. > > -Daniel > > > > Thanks for the reviews, Daniel. > > Took a closer look. I think if we cc: stable, this fix should accompany > commit 7eeaeb90a6a5 ("drm/file: Don't set master on in-kernel clients") > which moves the drm_master_open out from drm_file_alloc into > drm_open_helper. Ah right, please reference that commit with a Fixes: line. -Daniel > > > > --- > > > drivers/gpu/drm/drm_file.c | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c > > > index ed25168619fc..90b62f360da1 100644 > > > --- a/drivers/gpu/drm/drm_file.c > > > +++ b/drivers/gpu/drm/drm_file.c > > > @@ -282,9 +282,6 @@ void drm_file_free(struct drm_file *file) > > > drm_legacy_ctxbitmap_flush(dev, file); > > > - if (drm_is_primary_client(file)) > > > - drm_master_release(file); > > > - > > > if (dev->driver->postclose) > > > dev->driver->postclose(dev, file); > > > @@ -305,6 +302,9 @@ static void drm_close_helper(struct file *filp) > > > list_del(&file_priv->lhead); > > > mutex_unlock(&dev->filelist_mutex); > > > + if (drm_is_primary_client(file_priv)) > > > + drm_master_release(file_priv); > > > + > > > drm_file_free(file_priv); > > > } > > > -- > > > 2.25.1 > > > > > >
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index ed25168619fc..90b62f360da1 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -282,9 +282,6 @@ void drm_file_free(struct drm_file *file) drm_legacy_ctxbitmap_flush(dev, file); - if (drm_is_primary_client(file)) - drm_master_release(file); - if (dev->driver->postclose) dev->driver->postclose(dev, file); @@ -305,6 +302,9 @@ static void drm_close_helper(struct file *filp) list_del(&file_priv->lhead); mutex_unlock(&dev->filelist_mutex); + if (drm_is_primary_client(file_priv)) + drm_master_release(file_priv); + drm_file_free(file_priv); }
drm_master_release can be called on a drm_file without a master, which results in a null ptr dereference of file_priv->master->magic_map. The three cases are: 1. Error path in drm_open_helper drm_open(): drm_open_helper(): drm_master_open(): drm_new_set_master(); <--- returns -ENOMEM, drm_file.master not set drm_file_free(): drm_master_release(); <--- NULL ptr dereference (file_priv->master->magic_map) 2. Error path in mock_drm_getfile mock_drm_getfile(): anon_inode_getfile(); <--- returns error, drm_file.master not set drm_file_free(): drm_master_release(); <--- NULL ptr dereference (file_priv->master->magic_map) 3. In drm_client_close, as drm_client_open doesn't set up a master drm_file.master is set up in drm_open_helper through the call to drm_master_open, so we mirror it with a call to drm_master_release in drm_close_helper, and remove drm_master_release from drm_file_free to avoid the null ptr dereference. Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> --- drivers/gpu/drm/drm_file.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)