Re: [PATCHv2] media: videobuf2-dma-contig: fix bad kfree in vb2_dma_contig_clear_max_seg_size

On 27.05.2020 10:23, Tomi Valkeinen wrote:

Commit 9495b7e92f716ab2bd6814fab5e97ab4a39adfdd ("driver core: platform: Initialize dma_parms for platform devices") in v5.7-rc5 causes vb2_dma_contig_clear_max_seg_size() to kfree memory that was not allocated by vb2_dma_contig_set_max_seg_size().

The assumption in vb2_dma_contig_set_max_seg_size() seems to be that dev->dma_parms is always NULL when the driver is probed, and the case where dev->dma_parms has bee initialized by someone else than the driver (by calling vb2_dma_contig_set_max_seg_size) will cause a failure.

All the current users of these functions are platform devices, which now always have dma_parms set by the driver core. To fix the issue for v5.7, make vb2_dma_contig_set_max_seg_size() return an error if dma_parms is NULL to be on the safe side, and remove the kfree code from vb2_dma_contig_clear_max_seg_size().

For v5.8 we should remove the two functions and move the dma_set_max_seg_size() calls into the drivers.

Signed-off-by: Tomi Valkeinen tomi.valkeinen@ti.com Fixes: 9495b7e92f71 ("driver core: platform: Initialize dma_parms for platform devices") Cc: stable@vger.kernel.org

Acked-by: Marek Szyprowski m.szyprowski@samsung.com

---

Changes in v2:

• vb2_dma_contig_clear_max_seg_size to empty static inline

• Added cc: stable and fixes tag

  .../common/videobuf2/videobuf2-dma-contig.c | 20 ++----------------- include/media/videobuf2-dma-contig.h | 2 +- 2 files changed, 3 insertions(+), 19 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c index d3a3ee5b597b..f4b4a7c135eb 100644 --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c @@ -726,9 +726,8 @@ EXPORT_SYMBOL_GPL(vb2_dma_contig_memops); int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size) { if (!dev->dma_parms) {

• dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
  

• if (!dev->dma_parms)
  

• 	return -ENOMEM;
  

• dev_err(dev, "Failed to set max_seg_size: dma_parms is NULL\n");
  

• return -ENODEV;
  

  } if (dma_get_max_seg_size(dev) < size) return dma_set_max_seg_size(dev, size);

@@ -737,21 +736,6 @@ int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size) } EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size); -/*

• • vb2_dma_contig_clear_max_seg_size() - release resources for DMA parameters
• • @dev: device for configuring DMA parameters
• • This function releases resources allocated to configure DMA parameters
• • (see vb2_dma_contig_set_max_seg_size() function). It should be called from
• • device drivers on driver remove.
• */

-void vb2_dma_contig_clear_max_seg_size(struct device *dev) -{

• kfree(dev->dma_parms);
• dev->dma_parms = NULL;

-} -EXPORT_SYMBOL_GPL(vb2_dma_contig_clear_max_seg_size);

• MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2"); MODULE_AUTHOR("Pawel Osciak pawel@osciak.com"); MODULE_LICENSE("GPL");

diff --git a/include/media/videobuf2-dma-contig.h b/include/media/videobuf2-dma-contig.h index 5604818d137e..5be313cbf7d7 100644 --- a/include/media/videobuf2-dma-contig.h +++ b/include/media/videobuf2-dma-contig.h @@ -25,7 +25,7 @@ vb2_dma_contig_plane_dma_addr(struct vb2_buffer *vb, unsigned int plane_no) } int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size); -void vb2_dma_contig_clear_max_seg_size(struct device *dev); +static inline void vb2_dma_contig_clear_max_seg_size(struct device *dev) { } extern const struct vb2_mem_ops vb2_dma_contig_memops;

Best regards