linux-kernel - [PATCH] usb: udc: lpc32xx: fix bad bit shift operation

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Message-ID: <20191014191830.GA10721@embeddedor>
Date:   Mon, 14 Oct 2019 14:18:30 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Arnd Bergmann <arnd@...db.de>, Roland Stigge <stigge@...com.de>
Cc:     linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] usb: udc: lpc32xx: fix bad bit shift operation

It seems that the right variable to use in this case is *i*, instead of
*n*, otherwise there is an undefined behavior when right shifiting by more
than 31 bits when multiplying n by 8; notice that *n* can take values
equal or greater than 4 (4, 8, 16, ...).

Also, notice that under the current conditions (bl = 3), we are skiping
the handling of bytes 3, 7, 31... So, fix this by updating this logic
and limit *bl* up to 4 instead of up to 3.

This fix is based on function udc_stuff_fifo().

Addresses-Coverity-ID: 1454834 ("Bad bit shift operation")
Fixes: 24a28e428351 ("USB: gadget driver for LPC32xx")
Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/usb/gadget/udc/lpc32xx_udc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/udc/lpc32xx_udc.c b/drivers/usb/gadget/udc/lpc32xx_udc.c
index 2b1f3cc7819b..bf6c81e2f8cc 100644
--- a/drivers/usb/gadget/udc/lpc32xx_udc.c
+++ b/drivers/usb/gadget/udc/lpc32xx_udc.c
@@ -1177,11 +1177,11 @@ static void udc_pop_fifo(struct lpc32xx_udc *udc, u8 *data, u32 bytes)
 			tmp = readl(USBD_RXDATA(udc->udp_baseaddr));
 
 			bl = bytes - n;
-			if (bl > 3)
-				bl = 3;
+			if (bl > 4)
+				bl = 4;
 
 			for (i = 0; i < bl; i++)
-				data[n + i] = (u8) ((tmp >> (n * 8)) & 0xFF);
+				data[n + i] = (u8) ((tmp >> (i * 8)) & 0xFF);
 		}
 		break;
 
-- 
2.23.0