linux-kernel - Re: [PATCH v3 4/4] nvme: Allow reauth from sysfs

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Message-ID: <CAKmqyKNViQjZHyftdj7anoF1Wsf9qeRZQiZ9yfM_FsJAcmx7jg@mail.gmail.com>
Date: Tue, 18 Nov 2025 10:52:07 +1000
From: Alistair Francis <alistair23@...il.com>
To: Hannes Reinecke <hare@...e.de>
Cc: kbusch@...nel.org, axboe@...nel.dk, hch@....de, sagi@...mberg.me, 
	kch@...dia.com, linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v3 4/4] nvme: Allow reauth from sysfs

On Fri, Nov 14, 2025 at 5:15 PM Hannes Reinecke <hare@...e.de> wrote:
>
> On 11/14/25 05:58, alistair23@...il.com wrote:
> > From: Alistair Francis <alistair.francis@....com>
> >
> > Allow userspace to trigger a reauth (REPLACETLSPSK) from sysfs.
> > This can be done by writing  a zero to the sysfs file.
> >
> > echo 0 > /sys/devices/virtual/nvme-fabrics/ctl/nvme0/tls_configured_key
> >
> > Signed-off-by: Alistair Francis <alistair.francis@....com>
> > ---
> > v3:
> >   - Only trigger if a 0 is written to `tls_configured_key`
> >   - Add documentation
> > v2:
> >   - Trigger on any value written to `tls_configured_key`
> >
> >   Documentation/ABI/testing/sysfs-nvme | 13 +++++++++++
> >   drivers/nvme/host/sysfs.c            | 34 +++++++++++++++++++++++++++-
> >   2 files changed, 46 insertions(+), 1 deletion(-)
> >   create mode 100644 Documentation/ABI/testing/sysfs-nvme
> >
> > diff --git a/Documentation/ABI/testing/sysfs-nvme b/Documentation/ABI/testing/sysfs-nvme
> > new file mode 100644
> > index 000000000000..16aaf0dca9e2
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-nvme
> > @@ -0,0 +1,13 @@
> > +What:                /sys/devices/virtual/nvme-fabrics/ctl/.../tls_configured_key
> > +Date:                November 2025
> > +KernelVersion:       6.19
> > +Contact:     Linux NVMe mailing list <linux-nvme@...ts.infradead.org>
> > +Description:
> > +             The file is avaliable when using a secure concatanation
> > +             connection to a NVMe taget. Reading the file will return
> > +             the serial of the currently negotiated key.
> > +
> > +             Writing 0 to the file will trigger a PSK reauthentication
> > +             (REPLACETLSPSK) with the target. After a reauthentication
> > +             the value returned by tls_configured_key will be the new
> > +             serial.
> > diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
> > index 6d10e12136d0..7ff9a5053c3f 100644
> > --- a/drivers/nvme/host/sysfs.c
> > +++ b/drivers/nvme/host/sysfs.c
> > @@ -806,7 +806,39 @@ static ssize_t tls_configured_key_show(struct device *dev,
> >
> >       return sysfs_emit(buf, "%08x\n", key_serial(key));
> >   }
> > -static DEVICE_ATTR_RO(tls_configured_key);
> > +
> > +static ssize_t tls_configured_key_store(struct device *dev,
> > +                                     struct device_attribute *attr,
> > +                                     const char *buf, size_t count)
> > +{
> > +     struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
> > +     int error, qid;
> > +
> > +     error = kstrtoint(buf, 10, &qid);
> > +     if (error)
> > +             return error;
> > +
> > +     /*
> > +      * We currently only allow userspace to write a `0` indicating
> > +      * generate a new key.
> > +      */
> > +     if (!qid)
> > +             return -EINVAL;
> > +
> > +     if (!ctrl->opts || !ctrl->opts->concat)
> > +             return -EOPNOTSUPP;
> > +
> > +     error = nvme_auth_negotiate(ctrl, 0);
> > +     if (error < 0)
> > +             return error;
> > +
> > +     error = nvme_auth_wait(ctrl, 0);
> > +     if (error < 0)
> > +             return error;
> > +
> > +     return count;
> > +}
> > +static DEVICE_ATTR_RW(tls_configured_key);
> >
> >   static ssize_t tls_keyring_show(struct device *dev,
> >               struct device_attribute *attr, char *buf)
>
> Hmm.
> Now we are just running (re-) authentication, but that does
> not affect the TLS connection (which continues to use the
> original key). So you would need to reset the connection
> here to re-establish a new TLS connection.

Is the connection supposed to be reset? I don't see any mention of
that in the spec

>
> Also: if the authentication fails you need to tear down
> the connection (cf NVMe Base Spec 2.1, section 8.3.4.5.1
> Protocol Operations).

Ah good point

Alistair

>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke                  Kernel Storage Architect
> hare@...e.de                                +49 911 74053 688
> SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
> HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich