When the driver calls cx23885_risc_buffer() to prepare the buffer, the function call dma_alloc_coherent may fail, resulting in a empty buffer risc->cpu. Later when we free the buffer or access the buffer, null ptr deref is triggered. This bug is similar to the following one: https://git.linuxtv.org/media_stage.git/commit/?id=2b064d91440b33fba5b452f2d1b31f13ae911d71. We believe the bug can be also dynamically triggered from user side. Similarly, we fix this by checking the return value of cx23885_risc_buffer() and the value of risc->cpu before buffer free. Signed-off-by: harperchen <harperchen1110@xxxxxxxxx> --- drivers/media/pci/cx23885/cx23885-core.c | 4 +++- drivers/media/pci/cx23885/cx23885-video.c | 13 +++++++------ 2 files changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/media/pci/cx23885/cx23885-core.c b/drivers/media/pci/cx23885/cx23885-core.c index 9232a966bcab..2ce2914576cf 100644 --- a/drivers/media/pci/cx23885/cx23885-core.c +++ b/drivers/media/pci/cx23885/cx23885-core.c @@ -1325,7 +1325,9 @@ void cx23885_free_buffer(struct cx23885_dev *dev, struct cx23885_buffer *buf) { struct cx23885_riscmem *risc = &buf->risc; - dma_free_coherent(&dev->pci->dev, risc->size, risc->cpu, risc->dma); + if (risc->cpu) + dma_free_coherent(&dev->pci->dev, risc->size, risc->cpu, risc->dma); + memset(risc, 0, sizeof(*risc)); } static void cx23885_tsport_reg_dump(struct cx23885_tsport *port) diff --git a/drivers/media/pci/cx23885/cx23885-video.c b/drivers/media/pci/cx23885/cx23885-video.c index 3d03f5e95786..671fc0588e43 100644 --- a/drivers/media/pci/cx23885/cx23885-video.c +++ b/drivers/media/pci/cx23885/cx23885-video.c @@ -342,6 +342,7 @@ static int queue_setup(struct vb2_queue *q, static int buffer_prepare(struct vb2_buffer *vb) { + int ret; struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb); struct cx23885_dev *dev = vb->vb2_queue->drv_priv; struct cx23885_buffer *buf = @@ -358,12 +359,12 @@ static int buffer_prepare(struct vb2_buffer *vb) switch (dev->field) { case V4L2_FIELD_TOP: - cx23885_risc_buffer(dev->pci, &buf->risc, + ret = cx23885_risc_buffer(dev->pci, &buf->risc, sgt->sgl, 0, UNSET, buf->bpl, 0, dev->height); break; case V4L2_FIELD_BOTTOM: - cx23885_risc_buffer(dev->pci, &buf->risc, + ret = cx23885_risc_buffer(dev->pci, &buf->risc, sgt->sgl, UNSET, 0, buf->bpl, 0, dev->height); break; @@ -391,21 +392,21 @@ static int buffer_prepare(struct vb2_buffer *vb) line0_offset = 0; line1_offset = buf->bpl; } - cx23885_risc_buffer(dev->pci, &buf->risc, + ret = cx23885_risc_buffer(dev->pci, &buf->risc, sgt->sgl, line0_offset, line1_offset, buf->bpl, buf->bpl, dev->height >> 1); break; case V4L2_FIELD_SEQ_TB: - cx23885_risc_buffer(dev->pci, &buf->risc, + ret = cx23885_risc_buffer(dev->pci, &buf->risc, sgt->sgl, 0, buf->bpl * (dev->height >> 1), buf->bpl, 0, dev->height >> 1); break; case V4L2_FIELD_SEQ_BT: - cx23885_risc_buffer(dev->pci, &buf->risc, + ret = cx23885_risc_buffer(dev->pci, &buf->risc, sgt->sgl, buf->bpl * (dev->height >> 1), 0, buf->bpl, 0, @@ -418,7 +419,7 @@ static int buffer_prepare(struct vb2_buffer *vb) buf, buf->vb.vb2_buf.index, dev->width, dev->height, dev->fmt->depth, dev->fmt->fourcc, (unsigned long)buf->risc.dma); - return 0; + return ret; } static void buffer_finish(struct vb2_buffer *vb) -- 2.25.1
