On Wed, 27 Nov 2024 at 10:35, Laurent Pinchart laurent.pinchart@ideasonboard.com wrote:
Hi Ricardo,
Thank you for the patch.
On Wed, Nov 27, 2024 at 07:46:11AM +0000, Ricardo Ribalda wrote:
When an async control is written, we copy a pointer to the file handle that started the operation. That pointer will be used when the device is done. Which could be anytime in the future.
If the user closes that file descriptor, its structure will be freed, and there will be one dangling pointer per pending async control, that the driver will try to use.
Clean all the dangling pointers during release().
To avoid adding a performance penalty in the most common case (no async operation). A counter has been introduced with some logic to make sure that it is properly handled.
Cc: stable@vger.kernel.org Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives") Signed-off-by: Ricardo Ribalda ribalda@chromium.org
drivers/media/usb/uvc/uvc_ctrl.c | 40 ++++++++++++++++++++++++++++++++++++++-- drivers/media/usb/uvc/uvc_v4l2.c | 2 ++ drivers/media/usb/uvc/uvcvideo.h | 3 +++ 3 files changed, 43 insertions(+), 2 deletions(-)
diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c index 5d3a28edf7f0..51a53ad25e9c 100644 --- a/drivers/media/usb/uvc/uvc_ctrl.c +++ b/drivers/media/usb/uvc/uvc_ctrl.c @@ -1589,7 +1589,12 @@ void uvc_ctrl_status_event(struct uvc_video_chain *chain, mutex_lock(&chain->ctrl_mutex);
handle = ctrl->handle;
ctrl->handle = NULL;
if (handle) {ctrl->handle = NULL;WARN_ON(!handle->pending_async_ctrls);if (handle->pending_async_ctrls)handle->pending_async_ctrls--;}There's at least one other location where ctrl->handle is reset to NULL.
That assignment is not needed. I added a patch to remove it in the next version.
list_for_each_entry(mapping, &ctrl->info.mappings, list) { s32 value = __uvc_ctrl_get_value(mapping, data);@@ -2050,8 +2055,11 @@ int uvc_ctrl_set(struct uvc_fh *handle, mapping->set(mapping, value, uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));
if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS) {if (!ctrl->handle)handle->pending_async_ctrls++; ctrl->handle = handle;Is this protected by ctrl_mutex ?
yes, uvc_ctrl_set is only called by uvc_ioctl_s_try_ext_ctrls that calls uvc_ctrl_begin
I will send another patch to add an annotation to the function to make it explicit.
Please be careful about locking and race conditions, taking the time to double check will help getting your patches merged faster.
} ctrl->dirty = 1; ctrl->modified = 1;@@ -2774,6 +2782,34 @@ int uvc_ctrl_init_device(struct uvc_device *dev) return 0; }
+void uvc_ctrl_cleanup_fh(struct uvc_fh *handle) +{
struct uvc_entity *entity;guard(mutex)(&handle->chain->ctrl_mutex);if (!handle->pending_async_ctrls)return;list_for_each_entry(entity, &handle->chain->dev->entities, list) {int i;unsigned int
I wonder if these days you could event write
for (unsigned int i = 0; i < entity->ncontrols; ++i) {
for (i = 0; i < entity->ncontrols; ++i) {struct uvc_control *ctrl = &entity->controls[i];if (!ctrl->handle || ctrl->handle != handle)Given that handle can't be null, you can write
if (ctrl->handle != handle)
continue;ctrl->handle = NULL;if (WARN_ON(!handle->pending_async_ctrls))continue;Is this needed ? If we find more controls for this handle than pending_async_ctrls, decrementing it below 0 will case the WARN_ON() at the end of this function to trigger, isn't that enough ?
I want to know if the warning is triggered because I have too many pending_async_ctrls or too little.
handle->pending_async_ctrls--;}}WARN_ON(handle->pending_async_ctrls);+}
/*
- Cleanup device controls.
*/ diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c index 97c5407f6603..b425306a3b8c 100644 --- a/drivers/media/usb/uvc/uvc_v4l2.c +++ b/drivers/media/usb/uvc/uvc_v4l2.c @@ -652,6 +652,8 @@ static int uvc_v4l2_release(struct file *file)
uvc_dbg(stream->dev, CALLS, "%s\n", __func__);
uvc_ctrl_cleanup_fh(handle);/* Only free resources if this is a privileged handle. */ if (uvc_has_privileges(handle)) uvc_queue_release(&stream->queue);diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h index 07f9921d83f2..2f8a9c48e32a 100644 --- a/drivers/media/usb/uvc/uvcvideo.h +++ b/drivers/media/usb/uvc/uvcvideo.h @@ -612,6 +612,7 @@ struct uvc_fh { struct uvc_video_chain *chain; struct uvc_streaming *stream; enum uvc_handle_state state;
unsigned int pending_async_ctrls; /* Protected by ctrl_mutex. */The kernel does it the other way around, it lists in the documentation of the lock what data it protects.
};
struct uvc_driver { @@ -797,6 +798,8 @@ int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id, int uvc_xu_ctrl_query(struct uvc_video_chain *chain, struct uvc_xu_control_query *xqry);
+void uvc_ctrl_cleanup_fh(struct uvc_fh *handle);
/* Utility functions */ struct usb_host_endpoint *uvc_find_endpoint(struct usb_host_interface *alts, u8 epaddr);
-- Regards,
Laurent Pinchart
-- Ricardo Ribalda