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
>guangming.cao@xxxxxxxxxxxx
>Sent: Thursday, January 13, 2022 7:34 AM
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>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?

M

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