linux-kernel - [PATCH AUTOSEL 5.8 26/29] usb: cdns3: gadget: suspicious implicit sign extension

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Date:   Mon,  2 Nov 2020 20:19:25 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Peter Chen <peter.chen@....com>, Jun Li <jun.li@....com>,
        Sasha Levin <sashal@...nel.org>, linux-usb@...r.kernel.org
Subject: [PATCH AUTOSEL 5.8 26/29] usb: cdns3: gadget: suspicious implicit sign extension

From: Peter Chen <peter.chen@....com>

[ Upstream commit 5fca3f062879f8e5214c56f3e3e2be6727900f5d ]

The code:
trb->length = cpu_to_le32(TRB_BURST_LEN(priv_ep->trb_burst_size)
	       	| TRB_LEN(length));

TRB_BURST_LEN(priv_ep->trb_burst_size) may be overflow for int 32 if
priv_ep->trb_burst_size is equal or larger than 0x80;

Below is the Coverity warning:
sign_extension: Suspicious implicit sign extension: priv_ep->trb_burst_size
with type u8 (8 bits, unsigned) is promoted in priv_ep->trb_burst_size << 24
to type int (32 bits, signed), then sign-extended to type unsigned long
(64 bits, unsigned). If priv_ep->trb_burst_size << 24 is greater than 0x7FFFFFFF,
the upper bits of the result will all be 1.

To fix it, it needs to add an explicit cast to unsigned int type for ((p) << 24).

Reviewed-by: Jun Li <jun.li@....com>
Signed-off-by: Peter Chen <peter.chen@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/usb/cdns3/gadget.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/cdns3/gadget.h b/drivers/usb/cdns3/gadget.h
index 52765b098b9e1..28c4f6aca6891 100644
--- a/drivers/usb/cdns3/gadget.h
+++ b/drivers/usb/cdns3/gadget.h
@@ -1067,7 +1067,7 @@ struct cdns3_trb {
 #define TRB_TDL_SS_SIZE_GET(p)	(((p) & GENMASK(23, 17)) >> 17)
 
 /* transfer_len bitmasks - bits 31:24 */
-#define TRB_BURST_LEN(p)	(((p) << 24) & GENMASK(31, 24))
+#define TRB_BURST_LEN(p)	((unsigned int)((p) << 24) & GENMASK(31, 24))
 #define TRB_BURST_LEN_GET(p)	(((p) & GENMASK(31, 24)) >> 24)
 
 /* Data buffer pointer bitmasks*/
-- 
2.27.0