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V4L/DVB (13831): uvcvideo: Fix oops caused by a race condition in buffer dequeuing

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Buffers were marked as done before being removed from the IRQ queue. If
a userspace application dequeued and requeued the buffer fast enough
during that time window, the buffer could end up being deleted twice,
generating an oops in interrupt context.

Add a new state, UVC_BUF_STATE_READY, to mark buffers as ready for reuse
but not yet removed from the queue, and transition to UVC_BUF_STATE_DONE
only when the buffer is removed from the queue.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Laurent Pinchart 2009-12-16 21:20:45 -03:00 committed by Mauro Carvalho Chehab
parent 2c4d9de8ab
commit d7c0d43997
3 changed files with 18 additions and 14 deletions
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13
drivers/media/video/uvc/uvc_queue.c
View file

@ -59,9 +59,9 @@
* returns immediately.
*
* When the buffer is full, the completion handler removes it from the irq
* queue, marks it as ready (UVC_BUF_STATE_DONE) and wakes its wait queue.
* queue, marks it as done (UVC_BUF_STATE_DONE) and wakes its wait queue.
* At that point, any process waiting on the buffer will be woken up. If a
* process tries to dequeue a buffer after it has been marked ready, the
* process tries to dequeue a buffer after it has been marked done, the
* dequeing will succeed immediately.
*
* 2. Buffers are queued, user is waiting on a buffer and the device gets
@ -201,6 +201,7 @@ static void __uvc_query_buffer(struct uvc_buffer *buf,
break;
case UVC_BUF_STATE_QUEUED:
case UVC_BUF_STATE_ACTIVE:
case UVC_BUF_STATE_READY:
v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;
break;
case UVC_BUF_STATE_IDLE:
@ -295,13 +296,15 @@ static int uvc_queue_waiton(struct uvc_buffer *buf, int nonblocking)
{
if (nonblocking) {
return (buf->state != UVC_BUF_STATE_QUEUED &&
buf->state != UVC_BUF_STATE_ACTIVE)
buf->state != UVC_BUF_STATE_ACTIVE &&
buf->state != UVC_BUF_STATE_READY)
? 0 : -EAGAIN;
}
return wait_event_interruptible(buf->wait,
buf->state != UVC_BUF_STATE_QUEUED &&
buf->state != UVC_BUF_STATE_ACTIVE);
buf->state != UVC_BUF_STATE_ACTIVE &&
buf->state != UVC_BUF_STATE_READY);
}
/*
@ -348,6 +351,7 @@ int uvc_dequeue_buffer(struct uvc_video_queue *queue,
case UVC_BUF_STATE_IDLE:
case UVC_BUF_STATE_QUEUED:
case UVC_BUF_STATE_ACTIVE:
case UVC_BUF_STATE_READY:
default:
uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer state %u "
"(driver bug?).\n", buf->state);
@ -489,6 +493,7 @@ struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
spin_lock_irqsave(&queue->irqlock, flags);
list_del(&buf->queue);
buf->state = UVC_BUF_STATE_DONE;
if (!list_empty(&queue->irqqueue))
nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
queue);

14
drivers/media/video/uvc/uvc_video.c
View file

@ -441,7 +441,7 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
if (fid != stream->last_fid && buf->buf.bytesused != 0) {
uvc_trace(UVC_TRACE_FRAME, "Frame complete (FID bit "
"toggled).\n");
buf->state = UVC_BUF_STATE_DONE;
buf->state = UVC_BUF_STATE_READY;
return -EAGAIN;
}
@ -470,7 +470,7 @@ static void uvc_video_decode_data(struct uvc_streaming *stream,
/* Complete the current frame if the buffer size was exceeded. */
if (len > maxlen) {
uvc_trace(UVC_TRACE_FRAME, "Frame complete (overflow).\n");
buf->state = UVC_BUF_STATE_DONE;
buf->state = UVC_BUF_STATE_READY;
}
}
@ -482,7 +482,7 @@ static void uvc_video_decode_end(struct uvc_streaming *stream,
uvc_trace(UVC_TRACE_FRAME, "Frame complete (EOF found).\n");
if (data[0] == len)
uvc_trace(UVC_TRACE_FRAME, "EOF in empty payload.\n");
buf->state = UVC_BUF_STATE_DONE;
buf->state = UVC_BUF_STATE_READY;
if (stream->dev->quirks & UVC_QUIRK_STREAM_NO_FID)
stream->last_fid ^= UVC_STREAM_FID;
}
@ -568,8 +568,7 @@ static void uvc_video_decode_isoc(struct urb *urb, struct uvc_streaming *stream,
uvc_video_decode_end(stream, buf, mem,
urb->iso_frame_desc[i].actual_length);
if (buf->state == UVC_BUF_STATE_DONE ||
buf->state == UVC_BUF_STATE_ERROR)
if (buf->state == UVC_BUF_STATE_READY)
buf = uvc_queue_next_buffer(&stream->queue, buf);
}
}
@ -627,8 +626,7 @@ static void uvc_video_decode_bulk(struct urb *urb, struct uvc_streaming *stream,
if (!stream->bulk.skip_payload && buf != NULL) {
uvc_video_decode_end(stream, buf, stream->bulk.header,
stream->bulk.payload_size);
if (buf->state == UVC_BUF_STATE_DONE ||
buf->state == UVC_BUF_STATE_ERROR)
if (buf->state == UVC_BUF_STATE_READY)
buf = uvc_queue_next_buffer(&stream->queue,
buf);
}
@ -669,7 +667,7 @@ static void uvc_video_encode_bulk(struct urb *urb, struct uvc_streaming *stream,
stream->bulk.payload_size == stream->bulk.max_payload_size) {
if (buf->buf.bytesused == stream->queue.buf_used) {
stream->queue.buf_used = 0;
buf->state = UVC_BUF_STATE_DONE;
buf->state = UVC_BUF_STATE_READY;
uvc_queue_next_buffer(&stream->queue, buf);
stream->last_fid ^= UVC_STREAM_FID;
}

5
drivers/media/video/uvc/uvcvideo.h
View file

@ -365,8 +365,9 @@ enum uvc_buffer_state {
UVC_BUF_STATE_IDLE = 0,
UVC_BUF_STATE_QUEUED = 1,
UVC_BUF_STATE_ACTIVE = 2,
UVC_BUF_STATE_DONE = 3,
UVC_BUF_STATE_ERROR = 4,
UVC_BUF_STATE_READY = 3,
UVC_BUF_STATE_DONE = 4,
UVC_BUF_STATE_ERROR = 5,
};
struct uvc_buffer {