Hi folks, This is a refresh of my 2016 RFC patchset to start addressing object lifetime issues in Media controller. It further allows continuing work to address lifetime management of media entities. The underlying problem is described in detail in v4 of the previous RFC: <URL:https://lore.kernel.org/linux-media/20161108135438.GO3217@xxxxxxxxxxxxxxxxxxxxxxxxxx/>. In brief, there is currently no connection between releasing media device (and related) memory and IOCTL calls, meaning that there is a time window during which released kernel memory can be accessed, and that access can be triggered from the user space. The only reason why this is not a grave security issue is that it is not triggerable by the user alone but requires unbinding a device. That is still not an excuse for not fixing it. This set differs from the earlier RFC to address the issue in the following respects: - Make changes for ipu3-cio2 driver, too. - Continue to provide best effort attempt to keep the window between device removal and user space being able to access released memory as small as possible. This means the problem won't become worse for drivers for which Media device lifetime management has not been implemented. The latter is achieved by adding a new object, Media devnode compat reference, which is allocated, refcounted and eventually released by the Media controller framework itself, and where the information on registration and open filehandles is maintained. This is only done if the driver does not manage the lifetime of the media device itself, i.e. its release operation is NULL. Due to this, Media device file handles will also be introduced by this patchset. I thought the first user of this would be Media device events but it seems we already need them here. Both ipu3-cio2 and omap3isp drivers are relieved of devm_request_irq() use, as device_release() releases the resources before calling the driver's remove function. While further work will be required also on these drivers to safely stop he hardware at unbind time, I don't see a reason not to merge these patches now. Some patches are temporarily reverted in order to make reworks easier, then applied later on. I've tested this on ipu3-cio2 with and without the refcounting patch (media: ipu3-cio2: Release the cio2 device context by media device callback), including failures in a few parts of the driver initialisation process in the MC framework. Questions and comments are welcome. Daniel Axtens (1): media: uvcvideo: Refactor teardown of uvc on USB disconnect Laurent Pinchart (1): media: Add per-file-handle data support Logan Gunthorpe (1): media: utilize new cdev_device_add helper function Sakari Ailus (23): Revert "[media] media: fix media devnode ioctl/syscall and unregister race" Revert "media: utilize new cdev_device_add helper function" Revert "[media] media: fix use-after-free in cdev_put() when app exits after driver unbind" Revert "media: uvcvideo: Refactor teardown of uvc on USB disconnect" Revert "[media] media-device: dynamically allocate struct media_devnode" media device: Drop nop release callback media: Do not call cdev_device_del() if cdev_device_add() fails media-device: Delete character device early media: Split initialising and adding media devnode media: Shuffle functions around media device: Initialise media devnode in media_device_init() media device: Refcount the media device v4l: Acquire a reference to the media device for every video device media-device: Postpone graph object removal until free omap3isp: Release the isp device struct by media device callback omap3isp: Don't use devm_request_irq() media: Add nop implementations of media_device_{init,cleanup} media: ipu3-cio2: Call v4l2_device_unregister() earlier media: ipu3-cio2: Don't use devm_request_irq() media: ipu3-cio2: Release the cio2 device context by media device callback media: Maintain a list of open file handles in a media device media: Implement best effort media device removal safety sans refcounting media: Document how Media device resources are released Documentation/driver-api/media/mc-core.rst | 12 +- drivers/media/cec/core/cec-core.c | 2 +- drivers/media/mc/mc-device.c | 279 +++++++++++------- drivers/media/mc/mc-devnode.c | 94 +++--- drivers/media/pci/intel/ipu3/ipu3-cio2-main.c | 75 +++-- drivers/media/platform/ti/omap3isp/isp.c | 33 ++- drivers/media/usb/au0828/au0828-core.c | 4 +- drivers/media/usb/uvc/uvc_driver.c | 2 +- drivers/media/v4l2-core/v4l2-dev.c | 13 +- drivers/staging/media/sunxi/cedrus/cedrus.c | 2 +- include/media/media-device.h | 56 +++- include/media/media-devnode.h | 99 ++++--- include/media/media-fh.h | 32 ++ 13 files changed, 476 insertions(+), 227 deletions(-) create mode 100644 include/media/media-fh.h -- 2.30.2
