From: Scott Bauer <sbauer@plzdonthack.me>
To: David Kozub <zub@linux.fjfi.cvut.cz>
Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk, hch@infradead.org,
jonathan.derrick@intel.com
Subject: Re: [PATCH v2 11/16] block: sed-opal: ioctl for writing to shadow mbr
Date: Sun, 20 Jan 2019 16:20:00 -0500 [thread overview]
Message-ID: <20190120212000.GA4387@hacktheplanet> (raw)
In-Reply-To: <alpine.LRH.2.21.1901201045280.4278@linux.fjfi.cvut.cz>
On Sun, Jan 20, 2019 at 11:27:30AM +0100, David Kozub wrote:
> On Sat, 19 Jan 2019, Scott Bauer wrote:
>
> > On Thu, Jan 17, 2019 at 09:31:51PM +0000, David Kozub wrote:
> >
> > > +static int write_shadow_mbr(struct opal_dev *dev, void *data)
> > > +{
> > > + struct opal_shadow_mbr *shadow = data;
> > > + const u8 __user *src;
> > > + u8 *dst;
> > > + size_t off = 0;
> > > + u64 len;
> > > + int err = 0;
> > > +
> > > + /* do the actual transmission(s) */
> > > + src = (u8 *) shadow->data;
> > > + while (off < shadow->size) {
> > > + err = cmd_start(dev, opaluid[OPAL_MBR], opalmethod[OPAL_SET]);
> > > + add_token_u8(&err, dev, OPAL_STARTNAME);
> > > + add_token_u8(&err, dev, OPAL_WHERE);
> > > + add_token_u64(&err, dev, shadow->offset + off);
> > > + add_token_u8(&err, dev, OPAL_ENDNAME);
> > > +
> > > + add_token_u8(&err, dev, OPAL_STARTNAME);
> > > + add_token_u8(&err, dev, OPAL_VALUES);
> > > +
> > > + /*
> > > + * The bytestring header is either 1 or 2 bytes, so assume 2.
> > > + * There also needs to be enough space to accommodate the
> > > + * trailing OPAL_ENDNAME (1 byte) and tokens added by
> > > + * cmd_finalize.
> > > + */
> > > + len = min(remaining_size(dev) - (2+1+CMD_FINALIZE_BYTES_NEEDED),
> > > + (size_t)(shadow->size - off));
> >
> > What if remaining_size(dev) < 2 + 1 + CMD_FINALIZE_BYTES_NEEDED? If that's possible we
> > get min(UINT_MAX(ish) , some size larger than our remaining buffer) and that's not good.
>
> This is only possible for uselessly small values of IO_BUFFER_LENGTH, which
> is a compile-time value. Originally I thought it's OK as nobody would set
> the value so low. But on a second thought, after reading your comment, I
> think that even if IO_BUFFER_LENGTH was set to such a value, the code should
> fail gracefully.
Naw, just leave it the way it is. I didnt follow cmd_start down deep enough to realize we reset
the position on cmd_start, so there is no way for my scenario to happen. We'll never change IO_BUFFER_LENGTH
to something small. If someone wants to write a bug in their custom kernel, it's not our problem.
next prev parent reply other threads:[~2019-01-21 7:52 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-17 21:31 [PATCH v2 00/16] block: sed-opal: support shadow MBR done flag and write David Kozub
2019-01-17 21:31 ` [PATCH v2 01/16] block: sed-opal: fix typos and formatting David Kozub
2019-01-17 21:31 ` [PATCH v2 02/16] block: sed-opal: use correct macro for method length David Kozub
2019-01-17 21:31 ` [PATCH v2 03/16] block: sed-opal: unify space check in add_token_* David Kozub
2019-01-17 21:31 ` [PATCH v2 04/16] block: sed-opal: close parameter list in cmd_finalize David Kozub
2019-01-17 21:31 ` [PATCH v2 05/16] block: sed-opal: unify cmd start David Kozub
2019-01-17 21:31 ` [PATCH v2 06/16] block: sed-opal: unify error handling of responses David Kozub
2019-01-17 21:31 ` [PATCH v2 07/16] block: sed-opal: reuse response_get_token to decrease code duplication David Kozub
2019-01-17 21:31 ` [PATCH v2 08/16] block: sed-opal: print failed function address David Kozub
2019-01-17 21:31 ` [PATCH v2 09/16] block: sed-opal: split generation of bytestring header and content David Kozub
2019-01-17 21:31 ` [PATCH v2 10/16] block: sed-opal: add ioctl for done-mark of shadow mbr David Kozub
2019-01-17 21:31 ` [PATCH v2 11/16] block: sed-opal: ioctl for writing to " David Kozub
2019-01-19 17:15 ` Scott Bauer
2019-01-20 10:27 ` David Kozub
2019-01-20 21:20 ` Scott Bauer [this message]
2019-01-17 21:31 ` [PATCH v2 12/16] block: sed-opal: unify retrieval of table columns David Kozub
2019-01-17 21:31 ` [PATCH v2 13/16] block: sed-opal: check size of shadow mbr David Kozub
2019-01-19 17:29 ` Scott Bauer
2019-01-17 21:31 ` [PATCH v2 14/16] block: sed-opal: pass steps via argument rather than via opal_dev David Kozub
2019-01-17 21:31 ` [PATCH v2 15/16] block: sed-opal: don't repeat opal_discovery0 in each steps array David Kozub
2019-01-19 17:46 ` Scott Bauer
2019-01-20 20:23 ` David Kozub
2019-01-17 21:31 ` [PATCH v2 16/16] block: sed-opal: rename next to execute_steps David Kozub
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