Re: [PATCH v8 03/12] selftests: add tests_sysfs module

[Luis Chamberlain <mcgrof@kernel.org>]

On Tue, Oct 05, 2021 at 09:30:10AM -0700, Kees Cook wrote:
> On Mon, Sep 27, 2021 at 09:37:56AM -0700, Luis Chamberlain wrote:
> > --- /dev/null
> > +++ b/lib/test_sysfs.c
> > @@ -0,0 +1,921 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later OR copyleft-next-0.3.1
> > +/*
> > + * sysfs test driver
> > + *
> > + * Copyright (C) 2021 Luis Chamberlain <mcgrof@kernel.org>
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms of the GNU General Public License as published by the Free
> > + * Software Foundation; either version 2 of the License, or at your option any
> > + * later version; or, when distributed separately from the Linux kernel or
> > + * when incorporated into other software packages, subject to the following
> > + * license:
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms of copyleft-next (version 0.3.1 or later) as published
> > + * at http://copyleft-next.org/.
> 
> As Greg suggested, please drop the boilerplate here.

Sure, sorry for missing that fixed.

> > +static ssize_t config_show(struct device *dev,
> > +			   struct device_attribute *attr,
> > +			   char *buf)
> > +{
> > +	struct sysfs_test_device *test_dev = dev_to_test_dev(dev);
> > +	struct test_config *config = &test_dev->config;
> > +	int len = 0;
> > +
> > +	test_dev_config_lock(test_dev);
> > +
> > +	len += snprintf(buf, PAGE_SIZE,
> > +			"Configuration for: %s\n",
> > +			dev_name(dev));
> 
> Please use sysfs_emit() instead of snprintf().

Oh nice, done and fixed also in the other places.

> > +static int sysfs_test_dev_alloc_blockdev(struct sysfs_test_device *test_dev)
> > +{
> > +	int ret = -ENOMEM;
> > +
> > +	test_dev->disk = blk_alloc_disk(NUMA_NO_NODE);
> > +	if (!test_dev->disk) {
> > +		pr_err("Error allocating disk structure for device %d\n",
> > +		       test_dev->dev_idx);
> > +		goto out;
> > +	}
> > +
> > +	test_dev->disk->major = sysfs_test_major;
> > +	test_dev->disk->first_minor = test_dev->dev_idx + 1;
> > +	test_dev->disk->fops = &sysfs_testdev_ops;
> > +	test_dev->disk->private_data = test_dev;
> > +	snprintf(test_dev->disk->disk_name, 16, "test_sysfs%d",
> > +		 test_dev->dev_idx);
> 
> Prefer sizeof(test_dev->disk->disk_name) over open-coded "16".

Sure.

> > +static ssize_t read_reset_first_test_dev(struct file *file,
> > +					 char __user *user_buf,
> > +					 size_t count, loff_t *ppos)
> > +{
> > +	ssize_t len;
> > +	char buf[32];
> > +
> > +	reset_first_test_dev++;
> > +	len = sprintf(buf, "%d\n", reset_first_test_dev);
> 
> Even though it's safe as-is, I was going to suggest scnprintf() here
> (i.e. explicit bounds and a bounds-checked "len"). However, scnprintf()
> returns ssize_t, and there's no bounds checking in
> simple_read_from_buffer. That needs fixing (I'll send a patch).

OK we can later change it to scnprintf() once your patch gets merged.

> > --- /dev/null
> > +++ b/tools/testing/selftests/sysfs/sysfs.sh
> > @@ -0,0 +1,1208 @@
> > +#!/bin/bash
> > +# SPDX-License-Identifier: GPL-2.0-or-later
> > +# Copyright (C) 2021 Luis Chamberlain <mcgrof@kernel.org>
> > +#
> > +# This program is free software; you can redistribute it and/or modify it
> > +# under the terms of the GNU General Public License as published by the Free
> > +# Software Foundation; either version 2 of the License, or at your option any
> > +# later version; or, when distributed separately from the Linux kernel or
> > +# when incorporated into other software packages, subject to the following
> > +# license:
> > +#
> > +# This program is free software; you can redistribute it and/or modify it
> > +# under the terms of copyleft-next (version 0.3.1 or later) as published
> > +# at http://copyleft-next.org/.
> > +
> > +# This performs a series tests against the sysfs filesystem.
> 
> -boilerplate

Nuked.

> > +check_dmesg()
> > +{
> > +	# filter out intentional WARNINGs or Oopses
> > +	local filter=${1:-_check_dmesg_filter}
> > +
> > +	_dmesg_since_test_start | $filter >$seqres.dmesg
> > +	egrep -q -e "kernel BUG at" \
> > +	     -e "WARNING:" \
> > +	     -e "\bBUG:" \
> > +	     -e "Oops:" \
> > +	     -e "possible recursive locking detected" \
> > +	     -e "Internal error" \
> > +	     -e "(INFO|ERR): suspicious RCU usage" \
> > +	     -e "INFO: possible circular locking dependency detected" \
> > +	     -e "general protection fault:" \
> > +	     -e "BUG .* remaining" \
> > +	     -e "UBSAN:" \
> > +	     $seqres.dmesg
> 
> Is just looking for "call trace" sufficient here?

So far from my testing yes. This strategy is also borrowed from fstests
and that's what is done there, and so quite a lot of testing has been
done with that. If we are to consider an enhancement here we should then
also consider an enhancement welcome for fstests.

  Luis