Hi Tomi,
On 20.05.2020 15:15, 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@xxxxxx>
> ---
>
> Note: I have only fully tested this on linux-next, as the capture driver
> I use doesn't support unloading modules in v5.7.
>
> drivers/media/common/videobuf2/videobuf2-dma-contig.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> index d3a3ee5b597b..24f80b62ef94 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);
> @@ -747,8 +746,6 @@ EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
> */
> 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);
We don't need to export empty function imho. It can be made an empty
static inline in include/media/videobuf2-dma-contig.h.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
