[PATCH AUTOSEL 6.1 11/33] media: pci: tw68: Fix null-ptr-deref bug in buf prepare and finish

Sasha Levin
2023-05-01T03:10:37Z

From: harperchen <harperchen1110@gmail.com>

[ Upstream commit 1634b7adcc5bef645b3666fdd564e5952a9e24e0 ]

When the driver calls tw68_risc_buffer() to prepare the buffer, the
function call dma_alloc_coherent may fail, resulting in a empty buffer
buf->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 tw68_risc_buffer()
and the value of buf->cpu before buffer free.

Signed-off-by: harperchen <harperchen1110@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/pci/tw68/tw68-video.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/media/pci/tw68/tw68-video.c b/drivers/media/pci/tw68/tw68-video.c
index 0cbc5b038073b..773a18702d369 100644
--- a/drivers/media/pci/tw68/tw68-video.c
+++ b/drivers/media/pci/tw68/tw68-video.c
@@ -437,6 +437,7 @@ static void tw68_buf_queue(struct vb2_buffer *vb)
*/
static int tw68_buf_prepare(struct vb2_buffer *vb)
{
+ int ret;
struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
struct vb2_queue *vq = vb->vb2_queue;
struct tw68_dev *dev = vb2_get_drv_priv(vq);
@@ -452,30 +453,30 @@ static int tw68_buf_prepare(struct vb2_buffer *vb)
bpl = (dev->width * dev->fmt->depth) >> 3;
switch (dev->field) {
case V4L2_FIELD_TOP:
- tw68_risc_buffer(dev->pci, buf, dma->sgl,
+ ret = tw68_risc_buffer(dev->pci, buf, dma->sgl,
0, UNSET, bpl, 0, dev->height);
break;
case V4L2_FIELD_BOTTOM:
- tw68_risc_buffer(dev->pci, buf, dma->sgl,
+ ret = tw68_risc_buffer(dev->pci, buf, dma->sgl,
UNSET, 0, bpl, 0, dev->height);
break;
case V4L2_FIELD_SEQ_TB:
- tw68_risc_buffer(dev->pci, buf, dma->sgl,
+ ret = tw68_risc_buffer(dev->pci, buf, dma->sgl,
0, bpl * (dev->height >> 1),
bpl, 0, dev->height >> 1);
break;
case V4L2_FIELD_SEQ_BT:
- tw68_risc_buffer(dev->pci, buf, dma->sgl,
+ ret = tw68_risc_buffer(dev->pci, buf, dma->sgl,
bpl * (dev->height >> 1), 0,
bpl, 0, dev->height >> 1);
break;
case V4L2_FIELD_INTERLACED:
default:
- tw68_risc_buffer(dev->pci, buf, dma->sgl,
+ ret = tw68_risc_buffer(dev->pci, buf, dma->sgl,
0, bpl, bpl, bpl, dev->height >> 1);
break;
}
- return 0;
+ return ret;
}

static void tw68_buf_finish(struct vb2_buffer *vb)
@@ -485,7 +486,8 @@ static void tw68_buf_finish(struct vb2_buffer *vb)
struct tw68_dev *dev = vb2_get_drv_priv(vq);
struct tw68_buf *buf = container_of(vbuf, struct tw68_buf, vb);

- dma_free_coherent(&dev->pci->dev, buf->size, buf->cpu, buf->dma);
+ if (buf->cpu)
+ dma_free_coherent(&dev->pci->dev, buf->size, buf->cpu, buf->dma);
}

static int tw68_start_streaming(struct vb2_queue *q, unsigned int count)
--
2.39.2