Re: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation

["Christian König" <christian.koenig@amd.com>]

Am 13.01.22 um 14:00 schrieb Ruhl, Michael J:
>> -----Original Message-----
>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>> Ruhl, Michael J
>> Sent: Thursday, January 13, 2022 7:58 AM
>> To: guangming.cao@mediatek.com; sumit.semwal@linaro.org
>> Cc: jianjiao.zeng@mediatek.com; lmark@codeaurora.org;
>> wsd_upstream@mediatek.com; christian.koenig@amd.com; linux-
>> kernel@vger.kernel.org; dri-devel@lists.freedesktop.org;
>> yf.wang@mediatek.com; linaro-mm-sig@lists.linaro.org; linux-
>> mediatek@lists.infradead.org; libo.kang@mediatek.com;
>> benjamin.gaignard@linaro.org; bo.song@mediatek.com;
>> matthias.bgg@gmail.com; labbott@redhat.com;
>> mingyuan.ma@mediatek.com; linux-arm-kernel@lists.infradead.org; linux-
>> media@vger.kernel.org
>> Subject: RE: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>>
>>
>>> -----Original Message-----
>>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>>> guangming.cao@mediatek.com
>>> Sent: Thursday, January 13, 2022 7:34 AM
>>> To: sumit.semwal@linaro.org
>>> Cc: linux-arm-kernel@lists.infradead.org; mingyuan.ma@mediatek.com;
>>> Guangming <Guangming.Cao@mediatek.com>;
>>> wsd_upstream@mediatek.com; linux-kernel@vger.kernel.org; dri-
>>> devel@lists.freedesktop.org; linaro-mm-sig@lists.linaro.org;
>>> yf.wang@mediatek.com; libo.kang@mediatek.com;
>>> benjamin.gaignard@linaro.org; bo.song@mediatek.com;
>>> matthias.bgg@gmail.com; linux-mediatek@lists.infradead.org;
>>> lmark@codeaurora.org; labbott@redhat.com; christian.koenig@amd.com;
>>> jianjiao.zeng@mediatek.com; linux-media@vger.kernel.org
>>> Subject: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>>>
>>> From: Guangming <Guangming.Cao@mediatek.com>
>>>
>>> Add a size check for allocation since the allocation size is
>>> always less than the total DRAM size.
>>>
>>> Without this check, once the invalid size allocation runs on a process that
>>> can't be killed by OOM flow(such as "gralloc" on Android devices), it will
>>> cause a kernel exception, and to make matters worse, we can't find who are
>>> using
>>> so many memory with "dma_buf_debug_show" since the relevant dma-buf
>>> hasn't exported.
>>>
>>> To make OOM issue easier, maybe need dma-buf framework to dump the
>>> buffer size
>>> under allocating in "dma_buf_debug_show".
>>>
>>> Signed-off-by: Guangming <Guangming.Cao@mediatek.com>
>>> Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
>>> ---
>>> v3: 1. update patch, use right shift to replace division.
>>>     2. update patch, add reason in code and commit message.
>>> v2: 1. update size limitation as total_dram page size.
>>>     2. update commit message
>>> ---
>>> drivers/dma-buf/dma-heap.c | 10 ++++++++++
>>> 1 file changed, 10 insertions(+)
>>>
>>> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
>>> index 56bf5ad01ad5..1fd382712584 100644
>>> --- a/drivers/dma-buf/dma-heap.c
>>> +++ b/drivers/dma-buf/dma-heap.c
>>> @@ -55,6 +55,16 @@ static int dma_heap_buffer_alloc(struct dma_heap
>>> *heap, size_t len,
>>> 	struct dma_buf *dmabuf;
>>> 	int fd;
>>>
>>> +	/*
>>> +	 * Invalid size check. The "len" should be less than totalram.
>>> +	 *
>>> +	 * Without this check, once the invalid size allocation runs on a process
>>> that
>>> +	 * can't be killed by OOM flow(such as "gralloc" on Android devices), it
>>> will
>>> +	 * cause a kernel exception, and to make matters worse, we can't find
>>> who are using
>>> +	 * so many memory with "dma_buf_debug_show" since the relevant
>>> dma-buf hasn't exported.
>>> +	 */
>>> +	if (len >> PAGE_SHIFT > totalram_pages())
>> If your "heap" is from cma, is this still a valid check?
> And thinking a bit further, if I create a heap from something else (say device memory),
> you will need to be able to figure out the maximum allowable check for the specific
> heap.
>
> Maybe the heap needs a callback for max size?

Well we currently maintain a separate allocator and don't use dma-heap, 
but yes we have systems with 16GiB device and only 8GiB system memory so 
that check here is certainly not correct.

In general I would rather let the system run into -ENOMEM or -EINVAL 
from the allocator instead.

Regards,
Christian.

>
> m
>> M
>>
>>> +		return -EINVAL;
>>> 	/*
>>> 	 * Allocations from all heaps have to begin
>>> 	 * and end on page boundaries.
>>> --
>>> 2.17.1


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