lkml.org 
[lkml]   [2020]   [May]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Bad kfree of dma_parms in v5.7-rc5
From
Date
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

\
 
 \ /
  Last update: 2020-05-20 11:14    [W:0.065 / U:0.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site