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

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Message-ID: <24aaf108-0168-4a5c-57bb-cf24daefb990@linaro.org>
Date:   Fri, 25 Nov 2022 06:58:34 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        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 24/11/2022 18:03, Dmitry Osipenko wrote:
> 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.
thanks, that is true.



---srini

>