[media] bttv: fix mutex use before init (BZ#24602)

Fix a regression where bttv driver causes oopses when loading, since it
were using some non-initialized mutexes. While it would be possible to
fix the issue, there are some other lock troubles, like to the presence of
lock code at free_btres_lock().

It is possible to fix, but the better is to just use the core-assisted
locking schema. This way, V4L2 core will serialize access to all
ioctl's/open/close/mmap/read/poll operations, avoiding to have two
processes accessing the hardware at the same time. Also, as there's just
one lock, instead of 3, there's no risk of dead locks.

The net result is a cleaner code, with just one lock.

Reported-by: Dan Carpenter <[e-mail]>
Reported-by: Brandon Philips<[e-mail]>
Reported-by: Chris Clayton <[e-mail]>
Reported-by: Torsten Kaiser <[e-mail]>
Tested-by: Chris Clayton <[e-mail]>
Tested-by: Torsten Kaiser <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/video/bt8xx/bttv-driver.c

···
 		xbits |= RESOURCE_VIDEO_READ | RESOURCE_VIDEO_STREAM;
 
 	/* is it free? */
-	mutex_lock(&btv->lock);
 	if (btv->resources & xbits) {
 		/* no, someone else uses it */
 		goto fail;
···
 	/* it's free, grab it */
 	fh->resources  |= bit;
 	btv->resources |= bit;
-	mutex_unlock(&btv->lock);
 	return 1;
 
  fail:
-	mutex_unlock(&btv->lock);
 	return 0;
 }
 
···
 		/* trying to free ressources not allocated by us ... */
 		printk("bttv: BUG! (btres)\n");
 	}
-	mutex_lock(&btv->lock);
 	fh->resources  &= ~bits;
 	btv->resources &= ~bits;
 
···
 
 	if (0 == (bits & VBI_RESOURCES))
 		disclaim_vbi_lines(btv);
-
-	mutex_unlock(&btv->lock);
 }
 
 /* ----------------------------------------------------------------------- */
···
 
 		/* Make sure tvnorm and vbi_end remain consistent
 		   until we're done. */
-		mutex_lock(&btv->lock);
 
 		norm = btv->tvnorm;
 
 		/* In this mode capturing always starts at defrect.top
 		   (default VDELAY), ignoring cropping parameters. */
 		if (btv->vbi_end > bttv_tvnorms[norm].cropcap.defrect.top) {
-			mutex_unlock(&btv->lock);
 			return -EINVAL;
 		}
 
-		mutex_unlock(&btv->lock);
-
 		c.rect = bttv_tvnorms[norm].cropcap.defrect;
 	} else {
-		mutex_lock(&btv->lock);
-
 		norm = btv->tvnorm;
 		c = btv->crop[!!fh->do_crop];
-
-		mutex_unlock(&btv->lock);
 
 		if (width < c.min_scaled_width ||
 		    width > c.max_scaled_width ||
···
 	unsigned int i;
 	int err;
 
-	mutex_lock(&btv->lock);
 	err = v4l2_prio_check(&btv->prio, fh->prio);
 	if (err)
 		goto err;
···
 	set_tvnorm(btv, i);
 
 err:
-	mutex_unlock(&btv->lock);
 
 	return err;
 }
···
 	struct bttv *btv = fh->btv;
 	int rc = 0;
 
-	mutex_lock(&btv->lock);
 	if (i->index >= bttv_tvcards[btv->c.type].video_inputs) {
 		rc = -EINVAL;
 		goto err;
···
 	i->std = BTTV_NORMS;
 
 err:
-	mutex_unlock(&btv->lock);
 
 	return rc;
 }
···
 	struct bttv_fh *fh = priv;
 	struct bttv *btv = fh->btv;
 
-	mutex_lock(&btv->lock);
 	*i = btv->input;
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 
 	int err;
 
-	mutex_lock(&btv->lock);
 	err = v4l2_prio_check(&btv->prio, fh->prio);
 	if (unlikely(err))
 		goto err;
···
 	set_input(btv, i, btv->tvnorm);
 
 err:
-	mutex_unlock(&btv->lock);
 	return 0;
 }
 
···
 	if (unlikely(0 != t->index))
 		return -EINVAL;
 
-	mutex_lock(&btv->lock);
 	if (unlikely(btv->tuner_type == TUNER_ABSENT)) {
 		err = -EINVAL;
 		goto err;
···
 		btv->audio_mode_gpio(btv, t, 1);
 
 err:
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	struct bttv_fh *fh  = priv;
 	struct bttv *btv = fh->btv;
 
-	mutex_lock(&btv->lock);
 	f->type = btv->radio_user ? V4L2_TUNER_RADIO : V4L2_TUNER_ANALOG_TV;
 	f->frequency = btv->freq;
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	if (unlikely(f->tuner != 0))
 		return -EINVAL;
 
-	mutex_lock(&btv->lock);
 	err = v4l2_prio_check(&btv->prio, fh->prio);
 	if (unlikely(err))
 		goto err;
···
 	if (btv->has_matchbox && btv->radio_user)
 		tea5757_set_freq(btv, btv->freq);
 err:
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 
 	/* Make sure tvnorm, vbi_end and the current cropping parameters
 	   remain consistent until we're done. */
-	mutex_lock(&btv->lock);
 
 	b = &bttv_tvnorms[btv->tvnorm].cropcap.bounds;
 
···
 	rc = 0; /* success */
 
  fail:
-	mutex_unlock(&btv->lock);
 
 	return rc;
 }
···
 	if (V4L2_FIELD_ANY == field) {
 		__s32 height2;
 
-		mutex_lock(&fh->btv->lock);
 		height2 = fh->btv->crop[!!fh->do_crop].rect.height >> 1;
-		mutex_unlock(&fh->btv->lock);
 		field = (win->w.height > height2)
 			? V4L2_FIELD_INTERLACED
 			: V4L2_FIELD_TOP;
···
 		}
 	}
 
-	mutex_lock(&fh->cap.vb_lock);
 	/* clip against screen */
 	if (NULL != btv->fbuf.base)
 		n = btcx_screen_clips(btv->fbuf.fmt.width, btv->fbuf.fmt.height,
···
 		bttv_overlay_risc(btv, &fh->ov, fh->ovfmt, new);
 		retval = bttv_switch_overlay(btv,fh,new);
 	}
-	mutex_unlock(&fh->cap.vb_lock);
 	return retval;
 }
 
···
 	if (V4L2_FIELD_ANY == field) {
 		__s32 height2;
 
-		mutex_lock(&btv->lock);
 		height2 = btv->crop[!!fh->do_crop].rect.height >> 1;
-		mutex_unlock(&btv->lock);
 		field = (f->fmt.pix.height > height2)
 			? V4L2_FIELD_INTERLACED
 			: V4L2_FIELD_BOTTOM;
···
 	fmt = format_by_fourcc(f->fmt.pix.pixelformat);
 
 	/* update our state informations */
-	mutex_lock(&fh->cap.vb_lock);
 	fh->fmt              = fmt;
 	fh->cap.field        = f->fmt.pix.field;
 	fh->cap.last         = V4L2_FIELD_NONE;
···
 	btv->init.fmt        = fmt;
 	btv->init.width      = f->fmt.pix.width;
 	btv->init.height     = f->fmt.pix.height;
-	mutex_unlock(&fh->cap.vb_lock);
 
 	return 0;
 }
···
 	unsigned int i;
 	struct bttv_fh *fh = priv;
 
-	mutex_lock(&fh->cap.vb_lock);
 	retval = __videobuf_mmap_setup(&fh->cap, gbuffers, gbufsize,
 				     V4L2_MEMORY_MMAP);
 	if (retval < 0) {
-		mutex_unlock(&fh->cap.vb_lock);
 		return retval;
 	}
 
···
 	for (i = 0; i < gbuffers; i++)
 		mbuf->offsets[i] = i * gbufsize;
 
-	mutex_unlock(&fh->cap.vb_lock);
 	return 0;
 }
 #endif
···
 	int retval = 0;
 
 	if (on) {
-		mutex_lock(&fh->cap.vb_lock);
 		/* verify args */
 		if (unlikely(!btv->fbuf.base)) {
-			mutex_unlock(&fh->cap.vb_lock);
 			return -EINVAL;
 		}
 		if (unlikely(!fh->ov.setup_ok)) {
···
 		}
 		if (retval)
 			return retval;
-		mutex_unlock(&fh->cap.vb_lock);
 	}
 
 	if (!check_alloc_btres_lock(btv, fh, RESOURCE_OVERLAY))
 		return -EBUSY;
 
-	mutex_lock(&fh->cap.vb_lock);
 	if (on) {
 		fh->ov.tvnorm = btv->tvnorm;
 		new = videobuf_sg_alloc(sizeof(*new));
···
 
 	/* switch over */
 	retval = bttv_switch_overlay(btv, fh, new);
-	mutex_unlock(&fh->cap.vb_lock);
 	return retval;
 }
 
···
 	}
 
 	/* ok, accept it */
-	mutex_lock(&fh->cap.vb_lock);
 	btv->fbuf.base       = fb->base;
 	btv->fbuf.fmt.width  = fb->fmt.width;
 	btv->fbuf.fmt.height = fb->fmt.height;
···
 			retval = bttv_switch_overlay(btv, fh, new);
 		}
 	}
-	mutex_unlock(&fh->cap.vb_lock);
 	return retval;
 }
 
···
 	     c->id >= V4L2_CID_PRIVATE_LASTP1))
 		return -EINVAL;
 
-	mutex_lock(&btv->lock);
 	if (!btv->volume_gpio && (c->id == V4L2_CID_AUDIO_VOLUME))
 		*c = no_ctl;
 	else {
···
 
 		*c = (NULL != ctrl) ? *ctrl : no_ctl;
 	}
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	struct bttv_fh *fh = f;
 	struct bttv *btv = fh->btv;
 
-	mutex_lock(&btv->lock);
 	v4l2_video_std_frame_period(bttv_tvnorms[btv->tvnorm].v4l2_id,
 				    &parm->parm.capture.timeperframe);
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	if (0 != t->index)
 		return -EINVAL;
 
-	mutex_lock(&btv->lock);
 	t->rxsubchans = V4L2_TUNER_SUB_MONO;
 	bttv_call_all(btv, tuner, g_tuner, t);
 	strcpy(t->name, "Television");
···
 	if (btv->audio_mode_gpio)
 		btv->audio_mode_gpio(btv, t, 0);
 
-	mutex_unlock(&btv->lock);
 	return 0;
 }
 
···
 	struct bttv_fh *fh = f;
 	struct bttv *btv = fh->btv;
 
-	mutex_lock(&btv->lock);
 	*p = v4l2_prio_max(&btv->prio);
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	struct bttv *btv = fh->btv;
 	int	rc;
 
-	mutex_lock(&btv->lock);
 	rc = v4l2_prio_change(&btv->prio, &fh->prio, prio);
-	mutex_unlock(&btv->lock);
 
 	return rc;
 }
···
 	    cap->type != V4L2_BUF_TYPE_VIDEO_OVERLAY)
 		return -EINVAL;
 
-	mutex_lock(&btv->lock);
 	*cap = bttv_tvnorms[btv->tvnorm].cropcap;
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	   inconsistent with fh->width or fh->height and apps
 	   do not expect a change here. */
 
-	mutex_lock(&btv->lock);
 	crop->c = btv->crop[!!fh->do_crop].rect;
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	/* Make sure tvnorm, vbi_end and the current cropping
 	   parameters remain consistent until we're done. Note
 	   read() may change vbi_end in check_alloc_btres_lock(). */
-	mutex_lock(&btv->lock);
 	retval = v4l2_prio_check(&btv->prio, fh->prio);
 	if (0 != retval) {
-		mutex_unlock(&btv->lock);
 		return retval;
 	}
 
 	retval = -EBUSY;
 
 	if (locked_btres(fh->btv, VIDEO_RESOURCES)) {
-		mutex_unlock(&btv->lock);
 		return retval;
 	}
 
···
 
 	b_top = max(b->top, btv->vbi_end);
 	if (b_top + 32 >= b_bottom) {
-		mutex_unlock(&btv->lock);
 		return retval;
 	}
 
···
 
 	btv->crop[1] = c;
 
-	mutex_unlock(&btv->lock);
-
 	fh->do_crop = 1;
-
-	mutex_lock(&fh->cap.vb_lock);
 
 	if (fh->width < c.min_scaled_width) {
 		fh->width = c.min_scaled_width;
···
 		fh->height = c.max_scaled_height;
 		btv->init.height = c.max_scaled_height;
 	}
-
-	mutex_unlock(&fh->cap.vb_lock);
 
 	return 0;
 }
···
 		return videobuf_poll_stream(file, &fh->vbi, wait);
 	}
 
-	mutex_lock(&fh->cap.vb_lock);
 	if (check_btres(fh,RESOURCE_VIDEO_STREAM)) {
 		/* streaming capture */
 		if (list_empty(&fh->cap.stream))
···
 	else
 		rc = 0;
 err:
-	mutex_unlock(&fh->cap.vb_lock);
 	return rc;
 }
 
···
 	 * Let's first copy btv->init at fh, holding cap.vb_lock, and then work
 	 * with the rest of init, holding btv->lock.
 	 */
-	mutex_lock(&fh->cap.vb_lock);
 	*fh = btv->init;
-	mutex_unlock(&fh->cap.vb_lock);
 
 	fh->type = type;
 	fh->ov.setup_ok = 0;
 
-	mutex_lock(&btv->lock);
 	v4l2_prio_open(&btv->prio, &fh->prio);
 
 	videobuf_queue_sg_init(&fh->cap, &bttv_video_qops,
···
 			    V4L2_BUF_TYPE_VIDEO_CAPTURE,
 			    V4L2_FIELD_INTERLACED,
 			    sizeof(struct bttv_buffer),
-			    fh, NULL);
+			    fh, &btv->lock);
 	videobuf_queue_sg_init(&fh->vbi, &bttv_vbi_qops,
 			    &btv->c.pci->dev, &btv->s_lock,
 			    V4L2_BUF_TYPE_VBI_CAPTURE,
 			    V4L2_FIELD_SEQ_TB,
 			    sizeof(struct bttv_buffer),
-			    fh, NULL);
+			    fh, &btv->lock);
 	set_tvnorm(btv,btv->tvnorm);
 	set_input(btv, btv->input, btv->tvnorm);
 
···
 	bttv_vbi_fmt_reset(&fh->vbi_fmt, btv->tvnorm);
 
 	bttv_field_count(btv);
-	mutex_unlock(&btv->lock);
 	return 0;
 }
 
···
 	struct bttv_fh *fh = file->private_data;
 	struct bttv *btv = fh->btv;
 
-	mutex_lock(&btv->lock);
 	/* turn off overlay */
 	if (check_btres(fh, RESOURCE_OVERLAY))
 		bttv_switch_overlay(btv,fh,NULL);
···
 	 * videobuf uses cap.vb_lock - we should avoid holding btv->lock,
 	 * otherwise we may have dead lock conditions
 	 */
-	mutex_unlock(&btv->lock);
 	videobuf_mmap_free(&fh->cap);
 	videobuf_mmap_free(&fh->vbi);
-	mutex_lock(&btv->lock);
 	v4l2_prio_close(&btv->prio, fh->prio);
 	file->private_data = NULL;
 	kfree(fh);
···
 
 	if (!btv->users)
 		audio_mute(btv, 1);
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	if (unlikely(!fh))
 		return -ENOMEM;
 	file->private_data = fh;
-	mutex_lock(&fh->cap.vb_lock);
 	*fh = btv->init;
-	mutex_unlock(&fh->cap.vb_lock);
 
-	mutex_lock(&btv->lock);
 	v4l2_prio_open(&btv->prio, &fh->prio);
 
 	btv->radio_user++;
···
 	bttv_call_all(btv, tuner, s_radio);
 	audio_input(btv,TVAUDIO_INPUT_RADIO);
 
-	mutex_unlock(&btv->lock);
 	return 0;
 }
 
···
 	struct bttv *btv = fh->btv;
 	struct rds_command cmd;
 
-	mutex_lock(&btv->lock);
 	v4l2_prio_close(&btv->prio, fh->prio);
 	file->private_data = NULL;
 	kfree(fh);
···
 	btv->radio_user--;
 
 	bttv_call_all(btv, core, ioctl, RDS_CMD_CLOSE, &cmd);
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 		return -EINVAL;
 	if (0 != t->index)
 		return -EINVAL;
-	mutex_lock(&btv->lock);
 	strcpy(t->name, "Radio");
 	t->type = V4L2_TUNER_RADIO;
 
···
 
 	if (btv->audio_mode_gpio)
 		btv->audio_mode_gpio(btv, t, 0);
-
-	mutex_unlock(&btv->lock);
 
 	return 0;
 }
···
 	.open	  = radio_open,
 	.read     = radio_read,
 	.release  = radio_release,
-	.ioctl	  = video_ioctl2,
+	.unlocked_ioctl = video_ioctl2,
 	.poll     = radio_poll,
 };