linux-kernel - [PATCH 4.9 36/78] USB: sisusbvga: Fix a potential UB casued by left shifting a negative value

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Message-Id: <20200901150926.544654554@linuxfoundation.org>
Date:   Tue,  1 Sep 2020 17:10:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Changming Liu <charley.ashbringer@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 36/78] USB: sisusbvga: Fix a potential UB casued by left shifting a negative value

From: Changming Liu <charley.ashbringer@...il.com>

[ Upstream commit 2b53a19284f537168fb506f2f40d7fda40a01162 ]

The char buffer buf, receives data directly from user space,
so its content might be negative and its elements are left
shifted to form an unsigned integer.

Since left shifting a negative value is undefined behavior, thus
change the char to u8 to elimintate this UB.

Signed-off-by: Changming Liu <charley.ashbringer@...il.com>
Link: https://lore.kernel.org/r/20200711043018.928-1-charley.ashbringer@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/usb/misc/sisusbvga/sisusb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/misc/sisusbvga/sisusb.c b/drivers/usb/misc/sisusbvga/sisusb.c
index 895e8c0288cf9..30b3bdc4e6761 100644
--- a/drivers/usb/misc/sisusbvga/sisusb.c
+++ b/drivers/usb/misc/sisusbvga/sisusb.c
@@ -762,7 +762,7 @@ static int sisusb_write_mem_bulk(struct sisusb_usb_data *sisusb, u32 addr,
 	u8   swap8, fromkern = kernbuffer ? 1 : 0;
 	u16  swap16;
 	u32  swap32, flag = (length >> 28) & 1;
-	char buf[4];
+	u8 buf[4];
 
 	/* if neither kernbuffer not userbuffer are given, assume
 	 * data in obuf
-- 
2.25.1