drm_dev_is_unplugged() check is inherently racy as unplug can happen just after this check. Add DRM_UNPLUG_SAFE ioctl flag to keep the whole ioctl func call within drm_dev_enter() ... drm_dev_exit().
This could be enabled by drivers for individual ioctl's . Signed-off-by: Stanislaw Gruszka <[email protected]> --- drivers/gpu/drm/drm_ioctl.c | 22 +++++++++++++++------- include/drm/drm_ioctl.h | 7 +++++++ 2 files changed, 22 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index ca2a6e6101dc..9943f38c6b05 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -773,24 +773,32 @@ long drm_ioctl_kernel(struct file *file, drm_ioctl_t *func, void *kdata, { struct drm_file *file_priv = file->private_data; struct drm_device *dev = file_priv->minor->dev; - int retcode; + const bool global_mutex = drm_core_check_feature(dev, DRIVER_LEGACY) && + !(flags & DRM_UNLOCKED); + const bool unplug_safe = flags & DRM_UNPLUG_SAFE; + int retcode, idx; - if (drm_dev_is_unplugged(dev)) + if (!drm_dev_enter(dev, &idx)) return -ENODEV; + if (!unplug_safe) + drm_dev_exit(idx); retcode = drm_ioctl_permit(flags, file_priv); if (unlikely(retcode)) - return retcode; + goto out; - /* Enforce sane locking for modern driver ioctls. */ - if (likely(!drm_core_check_feature(dev, DRIVER_LEGACY)) || - (flags & DRM_UNLOCKED)) + if (likely(!global_mutex)) { retcode = func(dev, kdata, file_priv); - else { + } else { mutex_lock(&drm_global_mutex); retcode = func(dev, kdata, file_priv); mutex_unlock(&drm_global_mutex); } + +out: + if (unplug_safe) + drm_dev_exit(idx); + return retcode; } EXPORT_SYMBOL(drm_ioctl_kernel); diff --git a/include/drm/drm_ioctl.h b/include/drm/drm_ioctl.h index 6ed61c371f6c..894ce775ff12 100644 --- a/include/drm/drm_ioctl.h +++ b/include/drm/drm_ioctl.h @@ -130,6 +130,13 @@ enum drm_ioctl_flags { * not set DRM_AUTH because they do not require authentication. */ DRM_RENDER_ALLOW = BIT(5), + /** + * @DRM_UNPUG_SAFE: + * + * Whether &drm_ioctl_desc.func should be called as unplug critical + * section protected by drm_dev_enter() / drm_dev_exit() + */ + DRM_UNPLUG_SAFE = BIT(6), }; /** -- 2.25.1
