[PATCH v2] usb: musb: Fix musb_gadget.c rxstate may cause request->buf overflow problems

["Andy Guo (郭卫斌)" <guoweibin@inspur.com>]

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From: guoweibin <guoweibin@inspur.com>

when the rxstate function executes the 'goto buffer_aint_mapped' code
branch, it will always copy the fifocnt bytes data to request->buf,
which may cause request->buf out of bounds. for Ethernet-over-USB will
cause skb_over_panic when a packet larger than mtu is recived.

Fix it by add the length check :
fifocnt = min_t(unsigned, request->length - request->actual, fifocnt);

Signed-off-by: guoweibin <guoweibin@inspur.com>
---
 v2:
-fix format error
 drivers/usb/musb/musb_gadget.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index 51274b87f46c..4ad5a1f31d7e 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -760,6 +760,7 @@ static void rxstate(struct musb *musb, struct musb_request *req)
 			musb_writew(epio, MUSB_RXCSR, csr);
 
 buffer_aint_mapped:
+			fifo_count = min_t(unsigned, request->length - request->actual, fifo_count);
 			musb_read_fifo(musb_ep->hw_ep, fifo_count, (u8 *)
 					(request->buf + request->actual));
 			request->actual += fifo_count;

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