Invoke drm_plane_helper_funcs.end_fb_access before drm_atomic_helper_commit_hw_done(). The latter function hands over ownership of the plane state to the following commit, which might free it. Releasing resources in end_fb_access then operates on undefined state. This bug has been observed with non-blocking commits when they are being queued up quickly.

Here is an example stack trace from the bug report. The plane state has been free'd already, so the pages for drm_gem_fb_vunmap() are gone.

Unable to handle kernel paging request at virtual address 0000000100000049 [...] drm_gem_fb_vunmap+0x18/0x74 drm_gem_end_shadow_fb_access+0x1c/0x2c drm_atomic_helper_cleanup_planes+0x58/0xd8 drm_atomic_helper_commit_tail+0x90/0xa0 commit_tail+0x15c/0x188 commit_work+0x14/0x20

Fix this by running end_fb_access immediately after updating all planes in drm_atomic_helper_commit_planes(). The existing clean-up helper drm_atomic_helper_cleanup_planes() now only handles cleanup_fb.

For aborted commits, roll back from drm_atomic_helper_prepare_planes() in the new helper drm_atomic_helper_unprepare_planes(). This case is different from regular cleanup, as we have to release the new state; regular cleanup releases the old state. The new helper also invokes cleanup_fb for all planes.

The changes mostly involve DRM's atomic helpers. Only two drivers, i915 and nouveau, implement their own commit function. Update them to invoke drm_atomic_helper_unprepare_planes(). Drivers with custom commit_tail function do not require changes.

v4: * fix documentation (kernel test robot) v3: * add drm_atomic_helper_unprepare_planes() for rolling back * use correct state for end_fb_access v2: * fix test in drm_atomic_helper_cleanup_planes()

Reported-by: Alyssa Ross hi@alyssa.is Closes: https://lore.kernel.org/dri-devel/87leazm0ya.fsf@alyssa.is/ Suggested-by: Daniel Vetter daniel@ffwll.ch Fixes: 94d879eaf7fb ("drm/atomic-helper: Add {begin,end}_fb_access to plane helpers") Tested-by: Alyssa Ross hi@alyssa.is Reviewed-by: Alyssa Ross hi@alyssa.is Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Cc: stable@vger.kernel.org # v6.2+ --- drivers/gpu/drm/drm_atomic_helper.c | 78 +++++++++++++------- drivers/gpu/drm/i915/display/intel_display.c | 2 +- drivers/gpu/drm/nouveau/dispnv50/disp.c | 2 +- include/drm/drm_atomic_helper.h | 2 + 4 files changed, 56 insertions(+), 28 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index c3f677130def0..a920fbae714c8 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -2012,7 +2012,7 @@ int drm_atomic_helper_commit(struct drm_device *dev, return ret;

drm_atomic_helper_async_commit(dev, state); - drm_atomic_helper_cleanup_planes(dev, state); + drm_atomic_helper_unprepare_planes(dev, state);

return 0; } @@ -2072,7 +2072,7 @@ int drm_atomic_helper_commit(struct drm_device *dev, return 0;

err: - drm_atomic_helper_cleanup_planes(dev, state); + drm_atomic_helper_unprepare_planes(dev, state); return ret; } EXPORT_SYMBOL(drm_atomic_helper_commit); @@ -2650,6 +2650,39 @@ int drm_atomic_helper_prepare_planes(struct drm_device *dev, } EXPORT_SYMBOL(drm_atomic_helper_prepare_planes);

+/** + * drm_atomic_helper_unprepare_planes - release plane resources on aborts + * @dev: DRM device + * @state: atomic state object with old state structures + * + * This function cleans up plane state, specifically framebuffers, from the + * atomic state. It undoes the effects of drm_atomic_helper_prepare_planes() + * when aborting an atomic commit. For cleaning up after a successful commit + * use drm_atomic_helper_cleanup_planes(). + */ +void drm_atomic_helper_unprepare_planes(struct drm_device *dev, + struct drm_atomic_state *state) +{ + struct drm_plane *plane; + struct drm_plane_state *new_plane_state; + int i; + + for_each_new_plane_in_state(state, plane, new_plane_state, i) { + const struct drm_plane_helper_funcs *funcs = plane->helper_private; + + if (funcs->end_fb_access) + funcs->end_fb_access(plane, new_plane_state); + } + + for_each_new_plane_in_state(state, plane, new_plane_state, i) { + const struct drm_plane_helper_funcs *funcs = plane->helper_private; + + if (funcs->cleanup_fb) + funcs->cleanup_fb(plane, new_plane_state); + } +} +EXPORT_SYMBOL(drm_atomic_helper_unprepare_planes); + static bool plane_crtc_active(const struct drm_plane_state *state) { return state->crtc && state->crtc->state->active; @@ -2784,6 +2817,17 @@ void drm_atomic_helper_commit_planes(struct drm_device *dev,

funcs->atomic_flush(crtc, old_state); } + + /* + * Signal end of framebuffer access here before hw_done. After hw_done, + * a later commit might have already released the plane state. + */ + for_each_old_plane_in_state(old_state, plane, old_plane_state, i) { + const struct drm_plane_helper_funcs *funcs = plane->helper_private; + + if (funcs->end_fb_access) + funcs->end_fb_access(plane, old_plane_state); + } } EXPORT_SYMBOL(drm_atomic_helper_commit_planes);

@@ -2911,40 +2955,22 @@ EXPORT_SYMBOL(drm_atomic_helper_disable_planes_on_crtc); * configuration. Hence the old configuration must be perserved in @old_state to * be able to call this function. * - * This function must also be called on the new state when the atomic update - * fails at any point after calling drm_atomic_helper_prepare_planes(). + * This function may not be called on the new state when the atomic update + * fails at any point after calling drm_atomic_helper_prepare_planes(). Use + * drm_atomic_helper_unprepare_planes() in this case. */ void drm_atomic_helper_cleanup_planes(struct drm_device *dev, struct drm_atomic_state *old_state) { struct drm_plane *plane; - struct drm_plane_state *old_plane_state, *new_plane_state; + struct drm_plane_state *old_plane_state; int i;

- for_each_oldnew_plane_in_state(old_state, plane, old_plane_state, new_plane_state, i) { + for_each_old_plane_in_state(old_state, plane, old_plane_state, i) { const struct drm_plane_helper_funcs *funcs = plane->helper_private;

- if (funcs->end_fb_access) - funcs->end_fb_access(plane, new_plane_state); - } - - for_each_oldnew_plane_in_state(old_state, plane, old_plane_state, new_plane_state, i) { - const struct drm_plane_helper_funcs *funcs; - struct drm_plane_state *plane_state; - - /* - * This might be called before swapping when commit is aborted, - * in which case we have to cleanup the new state. - */ - if (old_plane_state == plane->state) - plane_state = new_plane_state; - else - plane_state = old_plane_state; - - funcs = plane->helper_private; - if (funcs->cleanup_fb) - funcs->cleanup_fb(plane, plane_state); + funcs->cleanup_fb(plane, old_plane_state); } } EXPORT_SYMBOL(drm_atomic_helper_cleanup_planes); diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c index 5cf162628b95e..ace834c9e8f9f 100644 --- a/drivers/gpu/drm/i915/display/intel_display.c +++ b/drivers/gpu/drm/i915/display/intel_display.c @@ -7354,7 +7354,7 @@ int intel_atomic_commit(struct drm_device *dev, struct drm_atomic_state *_state, for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) intel_color_cleanup_commit(new_crtc_state);

- drm_atomic_helper_cleanup_planes(dev, &state->base); + drm_atomic_helper_unprepare_planes(dev, &state->base); intel_runtime_pm_put(&dev_priv->runtime_pm, state->wakeref); return ret; } diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c index 11fe75b68e95c..8d37a694b7724 100644 --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c @@ -2476,7 +2476,7 @@ nv50_disp_atomic_commit(struct drm_device *dev,

err_cleanup: if (ret) - drm_atomic_helper_cleanup_planes(dev, state); + drm_atomic_helper_unprepare_planes(dev, state); done: pm_runtime_put_autosuspend(dev->dev); return ret; diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h index 536a0b0091c3a..006b5c977ad77 100644 --- a/include/drm/drm_atomic_helper.h +++ b/include/drm/drm_atomic_helper.h @@ -97,6 +97,8 @@ void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,

int drm_atomic_helper_prepare_planes(struct drm_device *dev, struct drm_atomic_state *state); +void drm_atomic_helper_unprepare_planes(struct drm_device *dev, + struct drm_atomic_state *state);

#define DRM_PLANE_COMMIT_ACTIVE_ONLY BIT(0) #define DRM_PLANE_COMMIT_NO_DISABLE_AFTER_MODESET BIT(1)