linux-kernel - Re: [PATCH 01/11] misc: fastrpc: Assert held reservation lock for dma-buf mmapping

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Message-ID: <a30bec0c-7471-a144-9a69-f59d952b8970@collabora.com>
Date:   Thu, 24 Nov 2022 21:03:18 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        gregkh@...uxfoundation.org,
        Christian König <christian.koenig@....com>
Cc:     linux-kernel@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH 01/11] misc: fastrpc: Assert held reservation lock for
 dma-buf mmapping

On 11/24/22 20:51, Srinivas Kandagatla wrote:
> From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> 
> When userspace mmaps dma-buf's fd, the dma-buf reservation lock must be
> held. Add locking sanity check to the dma-buf mmaping callback to ensure
> that the locking assumption won't regress in the future.
> 
> Suggested-by: Daniel Vetter <daniel@...ll.ch>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  drivers/misc/fastrpc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 80811e852d8f..c6b9ddaa698b 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -6,6 +6,7 @@
>  #include <linux/device.h>
>  #include <linux/dma-buf.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/dma-resv.h>
>  #include <linux/idr.h>
>  #include <linux/list.h>
>  #include <linux/miscdevice.h>
> @@ -692,6 +693,8 @@ static int fastrpc_mmap(struct dma_buf *dmabuf,
>  	struct fastrpc_buf *buf = dmabuf->priv;
>  	size_t size = vma->vm_end - vma->vm_start;
>  
> +	dma_resv_assert_held(dmabuf->resv);
> +
>  	return dma_mmap_coherent(buf->dev, vma, buf->virt,
>  				 FASTRPC_PHYS(buf->phys), size);
>  }

This patch was already applied to DRM tree together with the rest of
prerequisite dma-buf patches. IOW, it shouldn't be applied separately
via the misc tree.

-- 
Best regards,
Dmitry