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ad608fbcf1
The event subscriptions are added to the subscribed event list while
holding a spinlock, but that lock is subsequently released while still
accessing the subscription object. This makes it possible to unsubscribe
the event --- and freeing the subscription object's memory --- while
the subscription object is simultaneously accessed.
Prevent this by adding a mutex to serialise the event subscription and
unsubscription. This also gives a guarantee to the callback ops that the
add op has returned before the del op is called.
This change also results in making the elems field less special:
subscriptions are only added to the event list once they are fully
initialised.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: stable@vger.kernel.org # for 4.14 and up
Fixes: c3b5b0241f ("V4L/DVB: V4L: Events: Add backend")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
172 lines
4.6 KiB
C
172 lines
4.6 KiB
C
/*
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* v4l2-fh.h
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*
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* V4L2 file handle. Store per file handle data for the V4L2
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* framework. Using file handles is optional for the drivers.
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*
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* Copyright (C) 2009--2010 Nokia Corporation.
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*
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* Contact: Sakari Ailus <sakari.ailus@iki.fi>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#ifndef V4L2_FH_H
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#define V4L2_FH_H
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#include <linux/fs.h>
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#include <linux/kconfig.h>
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#include <linux/list.h>
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#include <linux/videodev2.h>
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struct video_device;
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struct v4l2_ctrl_handler;
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/**
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* struct v4l2_fh - Describes a V4L2 file handler
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*
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* @list: list of file handlers
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* @vdev: pointer to &struct video_device
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* @ctrl_handler: pointer to &struct v4l2_ctrl_handler
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* @prio: priority of the file handler, as defined by &enum v4l2_priority
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*
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* @wait: event' s wait queue
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* @subscribe_lock: serialise changes to the subscribed list; guarantee that
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* the add and del event callbacks are orderly called
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* @subscribed: list of subscribed events
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* @available: list of events waiting to be dequeued
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* @navailable: number of available events at @available list
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* @sequence: event sequence number
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*
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* @m2m_ctx: pointer to &struct v4l2_m2m_ctx
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*/
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struct v4l2_fh {
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struct list_head list;
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struct video_device *vdev;
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struct v4l2_ctrl_handler *ctrl_handler;
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enum v4l2_priority prio;
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/* Events */
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wait_queue_head_t wait;
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struct mutex subscribe_lock;
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struct list_head subscribed;
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struct list_head available;
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unsigned int navailable;
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u32 sequence;
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#if IS_ENABLED(CONFIG_V4L2_MEM2MEM_DEV)
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struct v4l2_m2m_ctx *m2m_ctx;
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#endif
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};
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/**
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* v4l2_fh_init - Initialise the file handle.
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*
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* @fh: pointer to &struct v4l2_fh
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* @vdev: pointer to &struct video_device
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*
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* Parts of the V4L2 framework using the
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* file handles should be initialised in this function. Must be called
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* from driver's v4l2_file_operations->open\(\) handler if the driver
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* uses &struct v4l2_fh.
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*/
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void v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev);
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/**
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* v4l2_fh_add - Add the fh to the list of file handles on a video_device.
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*
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* @fh: pointer to &struct v4l2_fh
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*
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* .. note::
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* The @fh file handle must be initialised first.
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*/
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void v4l2_fh_add(struct v4l2_fh *fh);
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/**
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* v4l2_fh_open - Ancillary routine that can be used as the open\(\) op
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* of v4l2_file_operations.
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*
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* @filp: pointer to struct file
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*
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* It allocates a v4l2_fh and inits and adds it to the &struct video_device
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* associated with the file pointer.
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*/
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int v4l2_fh_open(struct file *filp);
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/**
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* v4l2_fh_del - Remove file handle from the list of file handles.
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*
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* @fh: pointer to &struct v4l2_fh
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*
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* On error filp->private_data will be %NULL, otherwise it will point to
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* the &struct v4l2_fh.
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*
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* .. note::
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* Must be called in v4l2_file_operations->release\(\) handler if the driver
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* uses &struct v4l2_fh.
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*/
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void v4l2_fh_del(struct v4l2_fh *fh);
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/**
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* v4l2_fh_exit - Release resources related to a file handle.
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*
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* @fh: pointer to &struct v4l2_fh
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*
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* Parts of the V4L2 framework using the v4l2_fh must release their
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* resources here, too.
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*
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* .. note::
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* Must be called in v4l2_file_operations->release\(\) handler if the
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* driver uses &struct v4l2_fh.
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*/
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void v4l2_fh_exit(struct v4l2_fh *fh);
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/**
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* v4l2_fh_release - Ancillary routine that can be used as the release\(\) op
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* of v4l2_file_operations.
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*
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* @filp: pointer to struct file
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*
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* It deletes and exits the v4l2_fh associated with the file pointer and
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* frees it. It will do nothing if filp->private_data (the pointer to the
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* v4l2_fh struct) is %NULL.
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*
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* This function always returns 0.
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*/
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int v4l2_fh_release(struct file *filp);
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/**
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* v4l2_fh_is_singular - Returns 1 if this filehandle is the only filehandle
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* opened for the associated video_device.
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*
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* @fh: pointer to &struct v4l2_fh
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*
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* If @fh is NULL, then it returns 0.
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*/
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int v4l2_fh_is_singular(struct v4l2_fh *fh);
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/**
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* v4l2_fh_is_singular_file - Returns 1 if this filehandle is the only
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* filehandle opened for the associated video_device.
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*
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* @filp: pointer to struct file
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*
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* This is a helper function variant of v4l2_fh_is_singular() with uses
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* struct file as argument.
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*
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* If filp->private_data is %NULL, then it will return 0.
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*/
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static inline int v4l2_fh_is_singular_file(struct file *filp)
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{
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return v4l2_fh_is_singular(filp->private_data);
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}
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#endif /* V4L2_EVENT_H */
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