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SubjectRe: drivers/staging/greybus/bootrom.c:298:35-39: ERROR: fw is NULL but dereferenced.


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.

julia

>
> 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@linaro.org>
> > > :::::: CC: Greg Kroah-Hartman <gregkh@google.com>
> > >
> > > ---
> > > 0-DAY kernel test infrastructure Open Source Technology
> > > Center
> > > https://lists.01.org/pipermail/kbuild-all Intel
> > > Corporation
>

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