[PATCH 21/32] soc: qcom: apr: Use mem_to_flex_dup() with struct apr_rx_buf

[Kees Cook]

As part of the work to perform bounds checking on all memcpy() uses,
replace the open-coded a deserialization of bytes out of memory into a
trailing flexible array by using a flex_array.h helper to perform the
allocation, bounds checking, and copying.

Cc: Andy Gross <agross at kernel.org>
Cc: Bjorn Andersson <bjorn.andersson at linaro.org>
Cc: linux-arm-msm at vger.kernel.org
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 drivers/soc/qcom/apr.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/soc/qcom/apr.c b/drivers/soc/qcom/apr.c
index 3caabd873322..6cf6f6df276e 100644
--- a/drivers/soc/qcom/apr.c
+++ b/drivers/soc/qcom/apr.c
@@ -40,8 +40,8 @@ struct packet_router {
 
 struct apr_rx_buf {
 	struct list_head node;
-	int len;
-	uint8_t buf[];
+	DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(int, len);
+	DECLARE_FLEX_ARRAY_ELEMENTS(uint8_t, buf);
 };
 
 /**
@@ -162,7 +162,7 @@ static int apr_callback(struct rpmsg_device *rpdev, void *buf,
 				  int len, void *priv, u32 addr)
 {
 	struct packet_router *apr = dev_get_drvdata(&rpdev->dev);
-	struct apr_rx_buf *abuf;
+	struct apr_rx_buf *abuf = NULL;
 	unsigned long flags;
 
 	if (len <= APR_HDR_SIZE) {
@@ -171,13 +171,9 @@ static int apr_callback(struct rpmsg_device *rpdev, void *buf,
 		return -EINVAL;
 	}
 
-	abuf = kzalloc(sizeof(*abuf) + len, GFP_ATOMIC);
-	if (!abuf)
+	if (mem_to_flex_dup(&abuf, buf, len, GFP_ATOMIC))
 		return -ENOMEM;
 
-	abuf->len = len;
-	memcpy(abuf->buf, buf, len);
-
 	spin_lock_irqsave(&apr->rx_lock, flags);
 	list_add_tail(&abuf->node, &apr->rx_list);
 	spin_unlock_irqrestore(&apr->rx_lock, flags);
-- 
2.32.0