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

["Ruhl, Michael J" <michael.j.ruhl@intel.com>]

>-----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;
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>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?

M

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