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

[Ruhl, Michael J]

>-----Original Message-----
>From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
>Ruhl, Michael J
>Sent: Thursday, January 13, 2022 7:58 AM
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>Subject: RE: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>
>
>>-----Original Message-----
>>From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
>>guangming.cao@xxxxxxxxxxxx
>>Sent: Thursday, January 13, 2022 7:34 AM
>>To: sumit.semwal@xxxxxxxxxx
>>Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; mingyuan.ma@xxxxxxxxxxxx;
>>Guangming <Guangming.Cao@xxxxxxxxxxxx>;
>>wsd_upstream@xxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; dri-
>>devel@xxxxxxxxxxxxxxxxxxxxx; linaro-mm-sig@xxxxxxxxxxxxxxxx;
>>yf.wang@xxxxxxxxxxxx; libo.kang@xxxxxxxxxxxx;
>>benjamin.gaignard@xxxxxxxxxx; bo.song@xxxxxxxxxxxx;
>>matthias.bgg@xxxxxxxxx; linux-mediatek@xxxxxxxxxxxxxxxxxxx;
>>lmark@xxxxxxxxxxxxxx; labbott@xxxxxxxxxx; christian.koenig@xxxxxxx;
>>jianjiao.zeng@xxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx
>>Subject: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>>
>>From: Guangming <Guangming.Cao@xxxxxxxxxxxx>
>>
>>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@xxxxxxxxxxxx>
>>Signed-off-by: jianjiao zeng <jianjiao.zeng@xxxxxxxxxxxx>
>>---
>>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?

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