Messages in this thread | | | Subject | Re: Bad kfree of dma_parms in v5.7-rc5 | From | Marek Szyprowski <> | Date | Wed, 20 May 2020 11:13:24 +0200 |
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Hi Tomi,
On 20.05.2020 11:00, Tomi Valkeinen wrote: > Commit 9495b7e92f716ab2bd6814fab5e97ab4a39adfdd ("driver core: > platform: Initialize dma_parms for platform devices") v5.7-rc5 causes > at least some v4l2 platform drivers to break when freeing resources. > > E.g. drivers/media/platform/ti-vpe/cal.c uses > vb2_dma_contig_set_max_seg_size() and > vb2_dma_contig_clear_max_seg_size() to manage the dma_params, and > similar pattern is seen in other drivers too. > > After 9495b7e92f716ab2, vb2_dma_contig_set_max_seg_size() will not > allocate anything, but vb2_dma_contig_clear_max_seg_size() will still > kfree the dma_params. > > I'm not sure what's the proper fix here. A flag somewhere to indicate > that vb2_dma_contig_set_max_seg_size() did allocate, and thus > vb2_dma_contig_clear_max_seg_size() must free? > > Or drop the kzalloc and kfree totally, if dma_params is now supposed > to always be there?
Thanks for reporting this issue!
Once the mentioned commit has been merged, the code should assume that the platform devices does have a struct dma_params allocated, so the proper fix is to alloc dma_params only if the bus is not a platform bus:
if (!dev_is_platform(dev) && !dev->dma_parms) { dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
same check for the free path.
Would you like to send a patch for that?
Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
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