USB: core: Fix unterminated string returned by usb_string()
commit c01c348ecdc66085e44912c97368809612231520 upstream.
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: Alan Stern <stern@rowland.harvard.edu>
Reported-by: syzbot+b75b85111c10b8d680f1@syzkaller.appspotmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>
Change-Id: I29ccbe808127bfcb516d1e78eeecea863861bd51
1 file changed