USB: sisusbvga: Fix a potential UB casued by left shifting a negative value

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@gmail.com>
Link: https://lore.kernel.org/r/20200711043018.928-1-charley.ashbringer@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/misc/sisusbvga/sisusb.c b/drivers/usb/misc/sisusbvga/sisusb.c
index 88c4975e303d842ae6236778a0e3848a2477ae7e..f08de33d9ff383475b18908115a09248e157d164 100644 (file)
--- a/drivers/usb/misc/sisusbvga/sisusb.c
+++ b/drivers/usb/misc/sisusbvga/sisusb.c
@@ -761,7 +761,7 @@ 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