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>
diff --git a/drivers/media/video/gspca/gspca.c b/drivers/media/video/gspca/gspca.c
index 2dc7270..11b0e35 100644
--- a/drivers/media/video/gspca/gspca.c
+++ b/drivers/media/video/gspca/gspca.c
@@ -315,8 +315,6 @@
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 @@
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 @@
}
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
}
/* 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 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 @@
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);