Re: [kbuild-all] drivers/staging/greybus/bootrom.c:298:35-39: ERROR: fw is NULL but dereferenced.

[Fengguang Wu]

On Mon, Nov 28, 2016 at 09:59:52AM +0100, Julia Lawall wrote:
> On Mon, 28 Nov 2016, Fengguang Wu wrote:
>
> > On Sun, Nov 27, 2016 at 12:06:33PM +0100, Greg KH wrote:
> > > On Sun, Nov 27, 2016 at 07:11:46AM +0800, kbuild test robot wrote:
> > > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > > > master
> > > > head:   a0d60e62ea5c88a9823410e9d0929a513e29dea2
> > > > commit: f44dd184634d401f5cf88a6d8b4a60d5ff4f417f Merge greybus driver tree
> > > > into 4.8-rc6
> > > > date:   10 weeks ago
> > >
> > > This is a false-positive, sorry.
> >
> > Yes it's a false warning: ret != 0, so fw->size in the if test won't be
> > dereferenced.
> > Relevant code:
> >
> > if (!fw) {
> >                dev_err(dev, "%s: firmware not available\n", __func__);
> >                ret = -EINVAL;
> >                goto unlock;
> >        }
> > ...
> > unlock:
> >        mutex_unlock(&bootrom->mutex);
> >
> > queue_work:
> >        /* Refresh timeout */
> >        if (!ret && (offset + size == fw->size))
> >                next_request = NEXT_REQ_READY_TO_BOOT;
> >        else
> >                next_request = NEXT_REQ_GET_FIRMWARE;
> >
> > CC Julia for possible improvements to the coccinelle script.  If it's
> > not convenient to fix there I'll teach the robot to ignore this
> > particular false warning.
>
> This looks like it depends on analyzing the values of variables.
>
> It may be best to teach the robot to avoid this warning.  I can check
> these reports if needed for this problem.

OK. I'll send this kind of warnings to you instead of directly
reporting to the developer. Hope it's not a big burden on you.

Thanks,
Fengguang

> > > > coccinelle warnings: (new ones prefixed by >>)
> > > >
> > > > >> drivers/staging/greybus/bootrom.c:298:35-39: ERROR: fw is NULL but
> > > > dereferenced.
> > > >
> > > > vim +298 drivers/staging/greybus/bootrom.c
> > > >
> > > > 90f1b617 drivers/staging/greybus/firmware.c Viresh Kumar 2015-08-12  282
> > > > dev_err(dev, "%s: error allocating response\n", __func__);
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  283
> > > > ret = -ENOMEM;
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  284
> > > > goto unlock;
> > > > 90f1b617 drivers/staging/greybus/firmware.c Viresh Kumar 2015-08-12  285
> > > > }
> > > > 90f1b617 drivers/staging/greybus/firmware.c Viresh Kumar 2015-08-12  286
> > > > 90f1b617 drivers/staging/greybus/firmware.c Viresh Kumar 2015-08-12  287
> > > > firmware_response = op->response->payload;
> > > > 98645a9c drivers/staging/greybus/firmware.c Johan Hovold 2015-11-19  288
> > > > memcpy(firmware_response->data, fw->data + offset, size);
> > > > 90f1b617 drivers/staging/greybus/firmware.c Viresh Kumar 2015-08-12  289
> > > > fc41c2da drivers/staging/greybus/firmware.c Eli Sennesh  2016-01-08  290
> > > > dev_dbg(dev, "responding with firmware (offs = %u, size = %u)\n", offset,
> > > > fc41c2da drivers/staging/greybus/firmware.c Eli Sennesh  2016-01-08  291
> > > > size);
> > > > fc41c2da drivers/staging/greybus/firmware.c Eli Sennesh  2016-01-08  292
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  293
> > > > unlock:
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  294
> > > > mutex_unlock(&bootrom->mutex);
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  295
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  296
> > > > queue_work:
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  297
> > > > /* Refresh timeout */
> > > > a4293e1d drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-06-22 @298
> > > > if (!ret && (offset + size == fw->size))
> > > > a4293e1d drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-06-22  299
> > > > next_request = NEXT_REQ_READY_TO_BOOT;
> > > > a4293e1d drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-06-22  300
> > > > else
> > > > a4293e1d drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-06-22  301
> > > > next_request = NEXT_REQ_GET_FIRMWARE;
> > > > a4293e1d drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-06-22  302
> > > > dbb8cfeb drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-06-22  303
> > > > gb_bootrom_set_timeout(bootrom, next_request, NEXT_REQ_TIMEOUT_MS);
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  304
> > > > a956d939 drivers/staging/greybus/bootrom.c  Viresh Kumar 2016-05-09  305
> > > > return ret;
> > > > 90f1b617 drivers/staging/greybus/firmware.c Viresh Kumar 2015-08-12  306
> > > > }
> > > >
> > > > :::::: The code at line 298 was first introduced by commit
> > > > :::::: a4293e1d4e6416477976ee3bd248589d3fc4bb19 greybus: bootrom: Enhance
> > > > timeout error message
> > > >
> > > > :::::: TO: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> > > > :::::: CC: Greg Kroah-Hartman <gregkh@xxxxxxxxxx>
> > > >
> > > > ---
> > > > 0-DAY kernel test infrastructure                Open Source Technology
> > > > Center
> > > > https://lists.01.org/pipermail/kbuild-all                   Intel
> > > > Corporation
> _______________________________________________
> kbuild-all mailing list
> kbuild-all@xxxxxxxxxxxx
> https://lists.01.org/mailman/listinfo/kbuild-all