svn commit: r337887 - head/usr.sbin/bhyve

[Brooks Davis]

On Thu, Aug 16, 2018 at 05:23:26PM -0600, Warner Losh wrote:
> On Thu, Aug 16, 2018 at 5:16 PM, Brooks Davis <brooks at freebsd.org> wrote:
> 
> > On Fri, Aug 17, 2018 at 07:04:05AM +0800, Marcelo Araujo wrote:
> > > 2018-08-17 3:29 GMT+08:00 Rodney W. Grimes <freebsd at pdx.rh.cn85.dnsmgr.
> > net>:
> > >
> > > > > On Thu, Aug 16, 2018 at 11:06 AM, John-Mark Gurney <jmg at funkthat.com
> > >
> > > > wrote:
> > > > >
> > > > > > Marcelo Araujo wrote this message on Thu, Aug 16, 2018 at 06:31
> > +0000:
> > > > > > > Author: araujo
> > > > > > > Date: Thu Aug 16 06:31:54 2018
> > > > > > > New Revision: 337887
> > > > > > > URL: https://svnweb.freebsd.org/changeset/base/337887
> > > > > > >
> > > > > > > Log:
> > > > > > >   Add a comment explaining how the PSN works and why there is no
> > > > need for
> > > > > > >   a null terminator. Also mark CID 1394825 as intentional.
> > > > > > >
> > > > > > >   Reported by:        Coverity
> > > > > > >   CID:                1394825
> > > > > > >   MFC after:  1 week
> > > > > > >   Sponsored by:       iXsystems Inc.
> > > > > > >
> > > > > > > Modified:
> > > > > > >   head/usr.sbin/bhyve/pci_nvme.c
> > > > > > >
> > > > > > > Modified: head/usr.sbin/bhyve/pci_nvme.c
> > > > > > > ============================================================
> > > > > > ==================
> > > > > > > --- head/usr.sbin/bhyve/pci_nvme.c    Thu Aug 16 06:20:25 2018
> > > > > > (r337886)
> > > > > > > +++ head/usr.sbin/bhyve/pci_nvme.c    Thu Aug 16 06:31:54 2018
> > > > > > (r337887)
> > > > > > > @@ -1714,6 +1714,11 @@ pci_nvme_parse_opts(struct pci_nvme_softc
> > *sc,
> > > > > > char *o
> > > > > >
> > > > > > [...]
> > > > > >
> > > > > > >                       memset(sc->ctrldata.sn, 0, sizeof(sc->
> > > > ctrldata.sn
> > > > > > ));
> > > > > > >                       strncpy(sc->ctrldata.sn, config,
> > > > > > >                               sizeof(sc->ctrldata.sn));
> > > > > >
> > > > > > This memset is unneeded, as strncpy will write NUL bytes to fill
> > out
> > > > > > the buffer:
> > > > > > If src is less than len characters long, the remainder of
> > > > > >      dst is filled with `\0' characters.
> > > > > >
> > > > >
> > > > > It also looks like the comment was wrong. The newest NVMe standards
> > say
> > > > > these fields should be 7-bit and space-padded.
> > > >
> > > > lol, which is what the vendor that caused me grief with
> > > > ata serial numbers did decades ago.
> > > >
> > > > --
> > > > Rod Grimes
> > > > rgrimes at freebsd.org
> > > >
> > >
> > > I have discussed a bit with imp@, but I will drop the patch here to get
> > > other peoples opinion too.
> > > So, name space and firmware number also need to be padded with spaces.
> > >
> > > I couldn't think in any other better way to do that.
> > >
> > > Does this patch looks reasonable?
> > > https://people.freebsd.org/~araujo/pci_nvme.diff
> >
> > You should check that len<=dst_size and at least truncate rather than
> > overflowing.  If the strings from userspace you need to return or log an
> > error, if they come from the kernel, you can panic.
> 
> Help me understand, I thought that the strnlen bounded what was copied.

Apparently the standard calls for ' ' rather than '\0' padding.  The
prop memcpy+memset does the job, but contains potential overflows.

-- Brooks
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