[PATCH v1 1/2] dma-buf: Make locking consistent in dma_buf_detach()
Christian König
christian.koenig at amd.com
Thu Oct 27 06:13:38 UTC 2022
Am 27.10.22 um 00:46 schrieb Dmitry Osipenko:
> The dma_buf_detach() locks attach->dmabuf->resv and then unlocks
> dmabuf->resv, which could be a two different locks from a static
> code checker perspective. In particular this triggers Smatch to
> report the "double unlock" error. Make the locking pointers consistent.
>
> Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
> Link: https://lore.kernel.org/dri-devel/Y1fLfsccW3AS%2Fo+%2F@kili/
> Fixes: 809d9c72c2f8 ("dma-buf: Move dma_buf_attach() to dynamic locking specification")
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko at collabora.com>
It would be even cleaner if we completely drop the dmabuf parameter for
the function and just use the inside the attachment.
Anyway patch is Reviewed-by: Christian König <christian.koenig at amd.com>
for now, wider cleanups can come later on.
Regards,
Christian.
> ---
> drivers/dma-buf/dma-buf.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index c40d72d318fd..6e33ef4fde34 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -998,9 +998,10 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
> if (WARN_ON(!dmabuf || !attach))
> return;
>
> - dma_resv_lock(attach->dmabuf->resv, NULL);
> + dma_resv_lock(dmabuf->resv, NULL);
>
> if (attach->sgt) {
> + WARN_ON(dmabuf != attach->dmabuf);
>
> __unmap_dma_buf(attach, attach->sgt, attach->dir);
>
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