linux-kernel - [PATCH 3.16 069/136] usb: udc: lpc32xx: fix bad bit shift operation

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Date:   Tue, 17 Dec 2019 00:46:43 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH 3.16 069/136] usb: udc: lpc32xx: fix bad bit shift operation

3.16.80-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>

commit b987b66ac3a2bc2f7b03a0ba48a07dc553100c07 upstream.

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")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
Link: https://lore.kernel.org/r/20191014191830.GA10721@embeddedor
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/gadget/lpc32xx_udc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/usb/gadget/lpc32xx_udc.c
+++ b/drivers/usb/gadget/lpc32xx_udc.c
@@ -1228,11 +1228,11 @@ static void udc_pop_fifo(struct lpc32xx_
 			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;