SCSI: fix new bug in scsi_dev_info_list string matching

Commit b704f70c ("SCSI: fix bug in scsi_dev_info_list matching")
changed the way vendor- and model-string matching was carried out in the
routine that looks up entries in a SCSI devinfo list.  The new matching
code failed to take into account the case of a maximum-length string; in
such cases it could end up testing for a terminating '\0' byte beyond
the end of the memory allocated to the string.  This out-of-bounds bug
was detected by UBSAN.

I don't know if anybody has actually encountered this bug.  The symptom
would be that a device entry in the blacklist might not be matched
properly if it contained an 8-character vendor name or a 16-character
model name.  Such entries certainly exist in scsi_static_device_list.

This patch fixes the problem by adding a check for a maximum-length
string before the '\0' test.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Fixes: b704f70c ("SCSI: fix bug in scsi_dev_info_list matching")
Tested-by: Wilfried Klaebe <linux-kernel@lebenslange-mailadresse.de>
CC: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>