On Thu, May 03, 2018 at 08:35:30AM +0200, Daniel Vetter wrote:
On Wed, May 02, 2018 at 09:32:47PM +0300, Ville Syrjala wrote:
From: Ville Syrjälä ville.syrjala@linux.intel.com
Clear the old_state and new_state pointers for every object in drm_atomic_state_default_clear(). Otherwise drm_atomic_get_{new,old}_*_state() will hand out stale pointers to anyone who hasn't first confirmed that the object is in fact part of the current atomic transcation, if they are called after we've done the ww backoff dance while hanging on to the same drm_atomic_state.
For example, handle_conflicting_encoders() looks like it could hit this since it iterates the full connector list and just calls drm_atomic_get_new_connector_state() for each.
And I believe we have now witnessed this happening at least once in i915 check_digital_port_conflicts(). Commit 8b69449d2663 ("drm/i915: Remove last references to drm_atomic_get_existing* macros") changed the safe drm_atomic_get_existing_connector_state() to the unsafe drm_atomic_get_new_connector_state(), which opened the doors for this particular bug there as well.
Cc: stable@vger.kernel.org Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com Cc: Laurent Pinchart laurent.pinchart@ideasonboard.com Cc: Abhay Kumar abhay.kumar@intel.com Fixes: 581e49fe6b41 ("drm/atomic: Add new iterators over all state, v3.") Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com
Uh ... that's some bad oversight :-/
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
btw for stable we might want to split this into 1 patch for core objects and 1 patch for driver private stuff.
Good point. I forgot we did that after the new iterators were introduced. I'll do the split.
Feel free to do so while applying and keep my r-b. The fixes line for the 2nd patch would be:
Fixes: a4370c777406 ("drm/atomic: Make private objs proper objects") Cc: stable@vger.kernel.org # v4.14+
Ta.
Cheers, Daniel
drivers/gpu/drm/drm_atomic.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index 7d25c42f22db..c825c76edc1d 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -155,6 +155,8 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state) state->connectors[i].state); state->connectors[i].ptr = NULL; state->connectors[i].state = NULL;
state->connectors[i].old_state = NULL;state->connectors[i].new_state = NULL;@@ -169,6 +171,8 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state) state->crtcs[i].ptr = NULL; state->crtcs[i].state = NULL;
state->crtcs[i].old_state = NULL;state->crtcs[i].new_state = NULL;for (i = 0; i < config->num_total_plane; i++) { @@ -181,6 +185,8 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state) state->planes[i].state); state->planes[i].ptr = NULL; state->planes[i].state = NULL;
state->planes[i].old_state = NULL;state->planes[i].new_state = NULL;for (i = 0; i < state->num_private_objs; i++) { @@ -190,6 +196,8 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state) state->private_objs[i].state); state->private_objs[i].ptr = NULL; state->private_objs[i].state = NULL;
state->private_objs[i].old_state = NULL;state->private_objs[i].new_state = NULL;2.16.1
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-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch