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Subject[ 73/78] [media] uvcvideo: Fix race-related crash in uvc_video_clock_update()
3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

commit ed0ee0ce0a3224dab5caa088a5f8b6df25924276 upstream.

The driver frees the clock samples buffer before stopping the video
buffers queue. If a DQBUF call arrives in-between,
uvc_video_clock_update() will be called with a NULL clock samples
buffer, leading to a crash. This occurs very frequently when using the
webcam with the flash browser plugin.

Move clock initialization/cleanup to uvc_video_enable() in order to free
the clock samples buffer after the queue is stopped. Make sure the clock
is reset at resume time to avoid miscalculating timestamps.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/media/video/uvc/uvc_video.c | 50 +++++++++++++++++++++++-------------
1 file changed, 32 insertions(+), 18 deletions(-)

--- a/drivers/media/video/uvc/uvc_video.c
+++ b/drivers/media/video/uvc/uvc_video.c
@@ -468,22 +468,30 @@ uvc_video_clock_decode(struct uvc_stream
spin_unlock_irqrestore(&stream->clock.lock, flags);
}

-static int uvc_video_clock_init(struct uvc_streaming *stream)
+static void uvc_video_clock_reset(struct uvc_streaming *stream)
{
struct uvc_clock *clock = &stream->clock;

- spin_lock_init(&clock->lock);
clock->head = 0;
clock->count = 0;
- clock->size = 32;
clock->last_sof = -1;
clock->sof_offset = -1;
+}
+
+static int uvc_video_clock_init(struct uvc_streaming *stream)
+{
+ struct uvc_clock *clock = &stream->clock;
+
+ spin_lock_init(&clock->lock);
+ clock->size = 32;

clock->samples = kmalloc(clock->size * sizeof(*clock->samples),
GFP_KERNEL);
if (clock->samples == NULL)
return -ENOMEM;

+ uvc_video_clock_reset(stream);
+
return 0;
}

@@ -1424,8 +1432,6 @@ static void uvc_uninit_video(struct uvc_

if (free_buffers)
uvc_free_urb_buffers(stream);
-
- uvc_video_clock_cleanup(stream);
}

/*
@@ -1555,10 +1561,6 @@ static int uvc_init_video(struct uvc_str

uvc_video_stats_start(stream);

- ret = uvc_video_clock_init(stream);
- if (ret < 0)
- return ret;
-
if (intf->num_altsetting > 1) {
struct usb_host_endpoint *best_ep = NULL;
unsigned int best_psize = 3 * 1024;
@@ -1683,6 +1685,8 @@ int uvc_video_resume(struct uvc_streamin

stream->frozen = 0;

+ uvc_video_clock_reset(stream);
+
ret = uvc_commit_video(stream, &stream->ctrl);
if (ret < 0) {
uvc_queue_enable(&stream->queue, 0);
@@ -1819,25 +1823,35 @@ int uvc_video_enable(struct uvc_streamin
uvc_uninit_video(stream, 1);
usb_set_interface(stream->dev->udev, stream->intfnum, 0);
uvc_queue_enable(&stream->queue, 0);
+ uvc_video_clock_cleanup(stream);
return 0;
}

- ret = uvc_queue_enable(&stream->queue, 1);
+ ret = uvc_video_clock_init(stream);
if (ret < 0)
return ret;

+ ret = uvc_queue_enable(&stream->queue, 1);
+ if (ret < 0)
+ goto error_queue;
+
/* Commit the streaming parameters. */
ret = uvc_commit_video(stream, &stream->ctrl);
- if (ret < 0) {
- uvc_queue_enable(&stream->queue, 0);
- return ret;
- }
+ if (ret < 0)
+ goto error_commit;

ret = uvc_init_video(stream, GFP_KERNEL);
- if (ret < 0) {
- usb_set_interface(stream->dev->udev, stream->intfnum, 0);
- uvc_queue_enable(&stream->queue, 0);
- }
+ if (ret < 0)
+ goto error_video;
+
+ return 0;
+
+error_video:
+ usb_set_interface(stream->dev->udev, stream->intfnum, 0);
+error_commit:
+ uvc_queue_enable(&stream->queue, 0);
+error_queue:
+ uvc_video_clock_cleanup(stream);

return ret;
}



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