On Tue, 8 Aug 2017, Hannes Reinecke wrote:
> On 08/08/2017 05:25 PM, Alan Stern wrote:
> > On Tue, 8 Aug 2017, Hannes Reinecke wrote:
> >
> >> When checking the model and vendor string we need to use the
> >> minimum value of either string, otherwise we'll miss out on
> >> wildcard matches.
> >> And we should avoid matching anything with zero size as this
> >> match will be incorrect.
> >> Without this patch certain Hitachi arrays will not be presenting
> >> VPD pages correctly.
> >>
> >> Fixes: 5e7ff2c ("SCSI: fix new bug in scsi_dev_info_list string matching")
> >> Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
> >
> > This is very questionable. As described in commit b704f70ce200 ("SCSI:
> > fix bug in scsi_dev_info_list matching"), there are devices which have
> > vendor or model strings of length 0, and there are entries in the
> > global device list like that too. With this patch, such devices and
> > such entries would never match anything.
> >
> > Also, the idea of using the minimum length of either string doesn't
> > sound right. It would allow a device with string "abc" to match an
> > entry in the list with string "abcd", which would be wrong.
> >
> > Suggestion:
> >
> > Allow a device string to match a list entry if the lengths
> > are equal or the list entry is shorter (this would be a
> > wildcard match), but not if the list entry is longer. Here
> > the device string length is after leading and trailing blanks
> > have been removed.
> >
> > As a corollary, allow an empty device string to match an empty
> > list entry but nothing else.
> >
> > Alan Stern
> >
> Well, so far we haven't encountered any of those devices.
But what if we do in the future? The code should be correct for
anything.
> I _have_ validated the patch with the known problematic inquiry strings,
> namely
>
> "HITACHI" "OPEN-V"
> "Inateck" " "
> " " "Scanner"
> "Promise" "STEX"
>
> and it gives the correct result for all of these.
How can " " "Scanner" give the correct result? Oh, I see -- the
patch description and the code comment both say that empty strings
never match, but in fact they do -- you allow a match if either the
vendor or model string is empty, but not if they are both empty.
> If you have any inquiry strings for which this does _not_ produce the
> correct result please let me know.
What about "HITA" "OPEN-V"? Or "" "OPEN-V"? Both of these will match
the "HITACHI" "OPEN-" entry, but neither of them should.
What about "ABCD" "Scanner"? This will match the " " "Scanner"
entry, but it shouldn't.
Alan Stern
