V4L/DVB: gspca - main: Don't use the frame buffer flags

This patch fixes possible race conditions in queue management with SMP:
when a frame was completed, the irq function tried to use the next frame
buffer. At this time, it was possible that the application on an other
processor updated the frame pointer, making the image to point to a bad
buffer.
The patch contains two main changes:
- the image transfer uses the queue indexes which are protected against
  simultaneous memory access,
- the image pointer which is used for image concatenation is only set at
  interrupt level.
Some subdrivers which used the image pointer have been updated.

Reported-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/cpia1.c

@@ -1765,14 +1765,10 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 		atomic_set(&sd->cam_exposure, data[39] * 2);
 		atomic_set(&sd->fps, data[41]);
 
-		image = gspca_dev->image;
-		if (image == NULL) {
-			gspca_dev->last_packet_type = DISCARD_PACKET;
-			return;
-		}
-
 		/* Check for proper EOF for last frame */
-		if (gspca_dev->image_len > 4 &&
+		image = gspca_dev->image;
+		if (image != NULL &&
+		    gspca_dev->image_len > 4 &&
 		    image[gspca_dev->image_len - 4] == 0xff &&
 		    image[gspca_dev->image_len - 3] == 0xff &&
 		    image[gspca_dev->image_len - 2] == 0xff &&

drivers/media/video/gspca/gspca.c

@@ -315,8 +315,6 @@ static void fill_frame(struct gspca_dev *gspca_dev,
 		urb->status = 0;
 		goto resubmit;
 	}
-	if (gspca_dev->image == NULL)
-		gspca_dev->last_packet_type = DISCARD_PACKET;
 	pkt_scan = gspca_dev->sd_desc->pkt_scan;
 	for (i = 0; i < urb->number_of_packets; i++) {
 
@@ -428,16 +426,19 @@ void gspca_frame_add(struct gspca_dev *gspca_dev,
 
 	PDEBUG(D_PACK, "add t:%d l:%d",	packet_type, len);
 
-	/* check the availability of the frame buffer */
-	if (gspca_dev->image == NULL)
-		return;
-
 	if (packet_type == FIRST_PACKET) {
-		i = gspca_dev->fr_i;
+		i = atomic_read(&gspca_dev->fr_i);
+
+		/* if there are no queued buffer, discard the whole frame */
+		if (i == atomic_read(&gspca_dev->fr_q)) {
+			gspca_dev->last_packet_type = DISCARD_PACKET;
+			return;
+		}
 		j = gspca_dev->fr_queue[i];
 		frame = &gspca_dev->frame[j];
 		frame->v4l2_buf.timestamp = ktime_to_timeval(ktime_get());
 		frame->v4l2_buf.sequence = ++gspca_dev->sequence;
+		gspca_dev->image = frame->data;
 		gspca_dev->image_len = 0;
 	} else if (gspca_dev->last_packet_type == DISCARD_PACKET) {
 		if (packet_type == LAST_PACKET)
@@ -460,31 +461,24 @@ void gspca_frame_add(struct gspca_dev *gspca_dev,
 	}
 	gspca_dev->last_packet_type = packet_type;
 
-	/* if last packet, wake up the application and advance in the queue */
+	/* if last packet, invalidate packet concatenation until
+	 * next first packet, wake up the application and advance
+	 * in the queue */
 	if (packet_type == LAST_PACKET) {
-		i = gspca_dev->fr_i;
+		i = atomic_read(&gspca_dev->fr_i);
 		j = gspca_dev->fr_queue[i];
 		frame = &gspca_dev->frame[j];
 		frame->v4l2_buf.bytesused = gspca_dev->image_len;
 		frame->v4l2_buf.flags = (frame->v4l2_buf.flags
 					 | V4L2_BUF_FLAG_DONE)
 					& ~V4L2_BUF_FLAG_QUEUED;
+		i = (i + 1) % GSPCA_MAX_FRAMES;
+		atomic_set(&gspca_dev->fr_i, i);
 		wake_up_interruptible(&gspca_dev->wq);	/* event = new frame */
-		i = (i + 1) % gspca_dev->nframes;
-		gspca_dev->fr_i = i;
-		PDEBUG(D_FRAM, "frame complete len:%d q:%d i:%d o:%d",
-			frame->v4l2_buf.bytesused,
-			gspca_dev->fr_q,
-			i,
-			gspca_dev->fr_o);
-		j = gspca_dev->fr_queue[i];
-		frame = &gspca_dev->frame[j];
-		if ((frame->v4l2_buf.flags & BUF_ALL_FLAGS)
-					== V4L2_BUF_FLAG_QUEUED) {
-			gspca_dev->image = frame->data;
-		} else {
-			gspca_dev->image = NULL;
-		}
+		PDEBUG(D_FRAM, "frame complete len:%d",
+			frame->v4l2_buf.bytesused);
+		gspca_dev->image = NULL;
+		gspca_dev->image_len = 0;
 	}
 }
 EXPORT_SYMBOL(gspca_frame_add);
@@ -514,8 +508,8 @@ static int frame_alloc(struct gspca_dev *gspca_dev,
 	PDEBUG(D_STREAM, "frame alloc frsz: %d", frsz);
 	frsz = PAGE_ALIGN(frsz);
 	gspca_dev->frsz = frsz;
-	if (count > GSPCA_MAX_FRAMES)
-		count = GSPCA_MAX_FRAMES;
+	if (count >= GSPCA_MAX_FRAMES)
+		count = GSPCA_MAX_FRAMES - 1;
 	gspca_dev->frbuf = vmalloc_32(frsz * count);
 	if (!gspca_dev->frbuf) {
 		err("frame alloc failed");
@@ -534,11 +528,9 @@ static int frame_alloc(struct gspca_dev *gspca_dev,
 		frame->data = gspca_dev->frbuf + i * frsz;
 		frame->v4l2_buf.m.offset = i * frsz;
 	}
-	gspca_dev->fr_i = gspca_dev->fr_o = gspca_dev->fr_q = 0;
-	gspca_dev->image = NULL;
-	gspca_dev->image_len = 0;
-	gspca_dev->last_packet_type = DISCARD_PACKET;
-	gspca_dev->sequence = 0;
+	atomic_set(&gspca_dev->fr_q, 0);
+	atomic_set(&gspca_dev->fr_i, 0);
+	gspca_dev->fr_o = 0;
 	return 0;
 }
 
@@ -776,6 +768,12 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev)
 		goto out;
 	}
 
+	/* reset the streaming variables */
+	gspca_dev->image = NULL;
+	gspca_dev->image_len = 0;
+	gspca_dev->last_packet_type = DISCARD_PACKET;
+	gspca_dev->sequence = 0;
+
 	gspca_dev->usb_err = 0;
 
 	/* set the higher alternate setting and
@@ -1591,7 +1589,7 @@ static int vidioc_streamoff(struct file *file, void *priv,
 				enum v4l2_buf_type buf_type)
 {
 	struct gspca_dev *gspca_dev = priv;
-	int i, ret;
+	int ret;
 
 	if (buf_type != V4L2_BUF_TYPE_VIDEO_CAPTURE)
 		return -EINVAL;
@@ -1615,12 +1613,10 @@ static int vidioc_streamoff(struct file *file, void *priv,
 	gspca_stream_off(gspca_dev);
 	mutex_unlock(&gspca_dev->usb_lock);
 
-	/* empty the application queues */
-	for (i = 0; i < gspca_dev->nframes; i++)
-		gspca_dev->frame[i].v4l2_buf.flags &= ~BUF_ALL_FLAGS;
-	gspca_dev->fr_i = gspca_dev->fr_o = gspca_dev->fr_q = 0;
-	gspca_dev->last_packet_type = DISCARD_PACKET;
-	gspca_dev->sequence = 0;
+	/* empty the transfer queues */
+	atomic_set(&gspca_dev->fr_q, 0);
+	atomic_set(&gspca_dev->fr_i, 0);
+	gspca_dev->fr_o = 0;
 	ret = 0;
 out:
 	mutex_unlock(&gspca_dev->queue_lock);
@@ -1697,7 +1693,7 @@ static int vidioc_s_parm(struct file *filp, void *priv,
 	int n;
 
 	n = parm->parm.capture.readbuffers;
-	if (n == 0 || n > GSPCA_MAX_FRAMES)
+	if (n == 0 || n >= GSPCA_MAX_FRAMES)
 		parm->parm.capture.readbuffers = gspca_dev->nbufread;
 	else
 		gspca_dev->nbufread = n;
@@ -1800,21 +1796,17 @@ out:
 static int frame_wait(struct gspca_dev *gspca_dev,
 			int nonblock_ing)
 {
-	struct gspca_frame *frame;
-	int i, j, ret;
+	int i, ret;
 
 	/* check if a frame is ready */
 	i = gspca_dev->fr_o;
-	j = gspca_dev->fr_queue[i];
-	frame = &gspca_dev->frame[j];
-
-	if (!(frame->v4l2_buf.flags & V4L2_BUF_FLAG_DONE)) {
+	if (i == atomic_read(&gspca_dev->fr_i)) {
 		if (nonblock_ing)
 			return -EAGAIN;
 
 		/* wait till a frame is ready */
 		ret = wait_event_interruptible_timeout(gspca_dev->wq,
-			(frame->v4l2_buf.flags & V4L2_BUF_FLAG_DONE) ||
+			i != atomic_read(&gspca_dev->fr_i) ||
 			!gspca_dev->streaming || !gspca_dev->present,
 			msecs_to_jiffies(3000));
 		if (ret < 0)
@@ -1823,11 +1815,7 @@ static int frame_wait(struct gspca_dev *gspca_dev,
 			return -EIO;
 	}
 
-	gspca_dev->fr_o = (i + 1) % gspca_dev->nframes;
-	PDEBUG(D_FRAM, "frame wait q:%d i:%d o:%d",
-		gspca_dev->fr_q,
-		gspca_dev->fr_i,
-		gspca_dev->fr_o);
+	gspca_dev->fr_o = (i + 1) % GSPCA_MAX_FRAMES;
 
 	if (gspca_dev->sd_desc->dq_callback) {
 		mutex_lock(&gspca_dev->usb_lock);
@@ -1836,7 +1824,7 @@ static int frame_wait(struct gspca_dev *gspca_dev,
 			gspca_dev->sd_desc->dq_callback(gspca_dev);
 		mutex_unlock(&gspca_dev->usb_lock);
 	}
-	return j;
+	return gspca_dev->fr_queue[i];
 }
 
 /*
@@ -1941,15 +1929,9 @@ static int vidioc_qbuf(struct file *file, void *priv,
 	}
 
 	/* put the buffer in the 'queued' queue */
-	i = gspca_dev->fr_q;
+	i = atomic_read(&gspca_dev->fr_q);
 	gspca_dev->fr_queue[i] = index;
-	if (gspca_dev->fr_i == i)
-		gspca_dev->image = frame->data;
-	gspca_dev->fr_q = (i + 1) % gspca_dev->nframes;
-	PDEBUG(D_FRAM, "qbuf q:%d i:%d o:%d",
-		gspca_dev->fr_q,
-		gspca_dev->fr_i,
-		gspca_dev->fr_o);
+	atomic_set(&gspca_dev->fr_q, (i + 1) % GSPCA_MAX_FRAMES);
 
 	v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;
 	v4l2_buf->flags &= ~V4L2_BUF_FLAG_DONE;
@@ -2005,7 +1987,7 @@ static int read_alloc(struct gspca_dev *gspca_dev,
 static unsigned int dev_poll(struct file *file, poll_table *wait)
 {
 	struct gspca_dev *gspca_dev = file->private_data;
-	int i, ret;
+	int ret;
 
 	PDEBUG(D_FRAM, "poll");
 
@@ -2023,11 +2005,9 @@ static unsigned int dev_poll(struct file *file, poll_table *wait)
 	if (mutex_lock_interruptible(&gspca_dev->queue_lock) != 0)
 		return POLLERR;
 
-	/* check the next incoming buffer */
-	i = gspca_dev->fr_o;
-	i = gspca_dev->fr_queue[i];
-	if (gspca_dev->frame[i].v4l2_buf.flags & V4L2_BUF_FLAG_DONE)
-		ret = POLLIN | POLLRDNORM;	/* something to read */
+	/* check if an image has been received */
+	if (gspca_dev->fr_o != atomic_read(&gspca_dev->fr_i))
+		ret = POLLIN | POLLRDNORM;	/* yes */
 	else
 		ret = 0;
 	mutex_unlock(&gspca_dev->queue_lock);

drivers/media/video/gspca/gspca.h

@@ -178,11 +178,11 @@ struct gspca_dev {
 	u8 *image;				/* image beeing filled */
 	__u32 frsz;				/* frame size */
 	u32 image_len;				/* current length of image */
-	char nframes;				/* number of frames */
-	char fr_i;				/* frame being filled */
-	char fr_q;				/* next frame to queue */
-	char fr_o;				/* next frame to dequeue */
+	atomic_t fr_q;				/* next frame to queue */
+	atomic_t fr_i;				/* frame being filled */
 	signed char fr_queue[GSPCA_MAX_FRAMES];	/* frame queue */
+	char nframes;				/* number of frames */
+	u8 fr_o;				/* next frame to dequeue */
 	__u8 last_packet_type;
 	__s8 empty_packet;		/* if (-1) don't check empty packets */
 	__u8 streaming;

drivers/media/video/gspca/m5602/m5602_core.c

@@ -307,11 +307,6 @@ static void m5602_urb_complete(struct gspca_dev *gspca_dev,
 	} else {
 		int cur_frame_len;
 
-		if (gspca_dev->image == NULL) {
-			gspca_dev->last_packet_type = DISCARD_PACKET;
-			return;
-		}
-
 		cur_frame_len = gspca_dev->image_len;
 		/* Remove urb header */
 		data += 4;

drivers/media/video/gspca/ov534.c

@@ -988,8 +988,6 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 		/* If this packet is marked as EOF, end the frame */
 		} else if (data[1] & UVC_STREAM_EOF) {
 			sd->last_pts = 0;
-			if (gspca_dev->image == NULL)
-				goto discard;
 			if (gspca_dev->image_len + len - 12 !=
 			    gspca_dev->width * gspca_dev->height * 2) {
 				PDEBUG(D_PACK, "wrong sized frame");

drivers/media/video/gspca/pac7302.c

@@ -835,12 +835,6 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 	if (sof) {
 		int n, lum_offset, footer_length;
 
-		image = gspca_dev->image;
-		if (image == NULL) {
-			gspca_dev->last_packet_type = DISCARD_PACKET;
-			return;
-		}
-
 		/* 6 bytes after the FF D9 EOF marker a number of lumination
 		   bytes are send corresponding to different parts of the
 		   image, the 14th and 15th byte after the EOF seem to
@@ -856,7 +850,9 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 		} else {
 			gspca_frame_add(gspca_dev, INTER_PACKET, data, n);
 		}
-		if (gspca_dev->last_packet_type != DISCARD_PACKET
+
+		image = gspca_dev->image;
+		if (image != NULL
 		 && image[gspca_dev->image_len - 2] == 0xff
 		 && image[gspca_dev->image_len - 1] == 0xd9)
 			gspca_frame_add(gspca_dev, LAST_PACKET, NULL, 0);

drivers/media/video/gspca/pac7311.c

@@ -630,12 +630,6 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 	if (sof) {
 		int n, lum_offset, footer_length;
 
-		image = gspca_dev->image;
-		if (image == NULL) {
-			gspca_dev->last_packet_type = DISCARD_PACKET;
-			return;
-		}
-
 		/* 6 bytes after the FF D9 EOF marker a number of lumination
 		   bytes are send corresponding to different parts of the
 		   image, the 14th and 15th byte after the EOF seem to
@@ -651,7 +645,8 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 		} else {
 			gspca_frame_add(gspca_dev, INTER_PACKET, data, n);
 		}
-		if (gspca_dev->last_packet_type != DISCARD_PACKET
+		image = gspca_dev->image;
+		if (image != NULL
 		 && image[gspca_dev->image_len - 2] == 0xff
 		 && image[gspca_dev->image_len - 1] == 0xd9)
 			gspca_frame_add(gspca_dev, LAST_PACKET, NULL, 0);

drivers/media/video/gspca/sonixb.c

@@ -1254,10 +1254,6 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 		int used;
 		int size = cam->cam_mode[gspca_dev->curr_mode].sizeimage;
 
-		if (gspca_dev->image == NULL) {
-			gspca_dev->last_packet_type = DISCARD_PACKET;
-			return;
-		}
 		used = gspca_dev->image_len;
 		if (used + len > size)
 			len = size - used;

drivers/media/video/gspca/vc032x.c

@@ -3728,10 +3728,6 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 	if (sd->bridge == BRIDGE_VC0321) {
 		int size, l;
 
-		if (gspca_dev->image == NULL) {
-			gspca_dev->last_packet_type = DISCARD_PACKET;
-			return;
-		}
 		l = gspca_dev->image_len;
 		size = gspca_dev->frsz;
 		if (len > size - l)