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

[guangming.cao]

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