• Alan Stern's avatar
    USB: core: Fix unterminated string returned by usb_string() · c01c348e
    Alan Stern authored
    Some drivers (such as the vub300 MMC driver) expect usb_string() to
    return a properly NUL-terminated string, even when an error occurs.
    (In fact, vub300's probe routine doesn't bother to check the return
    code from usb_string().)  When the driver goes on to use an
    unterminated string, it leads to kernel errors such as
    stack-out-of-bounds, as found by the syzkaller USB fuzzer.
    
    An out-of-range string index argument is not at all unlikely, given
    that some devices don't provide string descriptors and therefore list
    0 as the value for their string indexes.  This patch makes
    usb_string() return a properly terminated empty string along with the
    -EINVAL error code when an out-of-range index is encountered.
    
    And since a USB string index is a single-byte value, indexes >= 256
    are just as invalid as values of 0 or below.
    Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    Reported-by: syzbot+b75b85111c10b8d680f1@syzkaller.appspotmail.com
    CC: <stable@vger.kernel.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    c01c348e
message.c 67.3 KB