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From: "Stephan Müller" <smueller@chronox.de>
To: Nicolai Stange <nstange@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-crypto@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	linux-api@vger.kernel.org,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Alexander E. Patrakov" <patrakov@gmail.com>,
	"Ahmed S. Darwish" <darwish.07@gmail.com>,
	"Theodore Y. Ts'o" <tytso@mit.edu>, Willy Tarreau <w@1wt.eu>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Vito Caputo <vcaputo@pengaru.com>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Jan Kara <jack@suse.cz>, Ray Strode <rstrode@redhat.com>,
	William Jon McCann <mccann@jhu.edu>,
	zhangjs <zachary@baishancloud.com>,
	Andy Lutomirski <luto@kernel.org>,
	Florian Weimer <fweimer@redhat.com>,
	Lennart Poettering <mzxreary@0pointer.de>,
	"Peter, Matthias" <matthias.peter@bsi.bund.de>,
	Marcelo Henrique Cerri <marcelo.cerri@canonical.com>,
	Roman Drahtmueller <draht@schaltsekun.de>,
	Neil Horman <nhorman@redhat.com>
Subject: Re: [PATCH v25 12/12] LRNG - add interface for gathering of raw entropy
Date: Thu, 21 Nov 2019 16:18:18 +0100
Message-ID: <23500762.5LfuSYdpsK@positron.chronox.de> (raw)
In-Reply-To: <87a78pl8xp.fsf@suse.de>

Am Donnerstag, 21. November 2019, 13:18:10 CET schrieb Nicolai Stange:

Hi Nicolai,

> Hi Stephan,
> 
> two general remarks on debugfs usage below
> 
> Stephan Müller <smueller@chronox.de> writes:
> > diff --git a/drivers/char/lrng/lrng_testing.c
> > b/drivers/char/lrng/lrng_testing.c new file mode 100644
> > index 000000000000..5c33d3bd2172
> > --- /dev/null
> > +++ b/drivers/char/lrng/lrng_testing.c
> 
> <snip>
> 
> > +/*
> > + * This data structure holds the dentry's of the debugfs files
> > establishing + * the interface to user space.
> > + */
> > +struct lrng_raw_debugfs {
> > +	struct dentry *lrng_raw_debugfs_root; /* root dentry */
> > +	struct dentry *lrng_raw_debugfs_lrng_raw; /* .../lrng_raw */
> > +};
> > +
> > +static struct lrng_raw_debugfs lrng_raw_debugfs;
> > +
> > +/* DebugFS operations and definition of the debugfs files */
> > +static ssize_t lrng_raw_read(struct file *file, char __user *to,
> > +			     size_t count, loff_t *ppos)
> > +{
> > +	loff_t pos = *ppos;
> > +	int ret;
> > +
> > +	if (!count)
> > +		return 0;
> > +	lrng_raw_entropy_init();
> > +	ret = lrng_raw_extract_user(to, count);
> > +	lrng_raw_entropy_fini();
> > +	if (ret < 0)
> > +		return ret;
> > +	count -= ret;
> > +	*ppos = pos + count;
> > +	return ret;
> > +}
> > +
> > +/* Module init: allocate memory, register the debugfs files */
> > +static int lrng_raw_debugfs_init(void)
> > +{
> > +	lrng_raw_debugfs.lrng_raw_debugfs_root =
> > +		debugfs_create_dir(KBUILD_MODNAME, NULL);
> > +	if (IS_ERR(lrng_raw_debugfs.lrng_raw_debugfs_root)) {
> > +		lrng_raw_debugfs.lrng_raw_debugfs_root = NULL;
> > +		return PTR_ERR(lrng_raw_debugfs.lrng_raw_debugfs_root);
> > +	}
> 
> I think pointers returned by the debugfs API are not supposed to get
> checked for NULL/IS_ERR(), c.f commit ff9fb72bc077 ("debugfs: return
> error values, not NULL") or the the output from
> 
>   git log --pretty=oneline | grep 'no need to check return value of
> debugfs_create'
> 
> (Also the above code is dubious: you're effectively returning
>  PTR_ERR(NULL)).

Removed the check compliant to the mentioned patches.
> 
> > +	return 0;
> > +}
> > +
> > +static struct file_operations lrng_raw_name_fops = {
> > +	.owner = THIS_MODULE,
> > +	.read = lrng_raw_read,
> > +};
> > +
> > +static int lrng_raw_debugfs_init_name(void)
> > +{
> > +	lrng_raw_debugfs.lrng_raw_debugfs_lrng_raw =
> > +		debugfs_create_file("lrng_raw", 0400,
> > +				    lrng_raw_debugfs.lrng_raw_debugfs_root,
> > +				    NULL, &lrng_raw_name_fops);q
> 
> CONFIG_LRNG_TESTING is a bool and thus, this debugfs file can't ever get
> removed. Even if it could, this inode hasn't got any data associated
> with it and so file removal would not be a problem for lrng_raw_read().

Correct.
> 
> Please consider using debugfs_create_file_unsafe() instead to save
> debugfs from kmalloc()ing a proxy file_operations protecting your fops
> against concurrent file removal.

Yes, you are correct. Changed.
> 
> > +	if (IS_ERR(lrng_raw_debugfs.lrng_raw_debugfs_lrng_raw)) {
> > +		lrng_raw_debugfs.lrng_raw_debugfs_lrng_raw = NULL;
> > +		return PTR_ERR(lrng_raw_debugfs.lrng_raw_debugfs_lrng_raw);
> > +	}
> 
> Same comment regarding return value checking applies here.

Same here: I removed the check.

With that, I also removed the static variable to maintain the two dentries 
following the examples seen in other kernel code. Also, the __exit function is 
removed as we do not need it as you pointed out.

Thanks a lot.
> 
> Thanks,
> 
> Nicolai
> 
> > +	return 0;
> > +}
> > +
> > +static int __init lrng_raw_init(void)
> > +{
> > +	int ret = lrng_raw_debugfs_init();
> > +
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ret = lrng_raw_debugfs_init_name();
> > +	if (ret < 0)
> > +		debugfs_remove_recursive(
> > +					lrng_raw_debugfs.lrng_raw_debugfs_root);
> > +
> > +	return ret;
> > +}
> > +
> > +static void __exit lrng_raw_exit(void)
> > +{
> > +	debugfs_remove_recursive(lrng_raw_debugfs.lrng_raw_debugfs_root);
> > +}
> > +
> > +module_init(lrng_raw_init);
> > +module_exit(lrng_raw_exit);
> > +
> > +MODULE_LICENSE("Dual BSD/GPL");
> > +MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
> > +MODULE_DESCRIPTION("Kernel module for gathering raw entropy");


Ciao
Stephan



  reply index

Thread overview: 162+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-11 18:17 [PATCH v24 00/12] /dev/random - a new approach with full SP800-90B compliance Stephan Müller
2019-11-11 18:18 ` [PATCH v24 01/12] Linux Random Number Generator Stephan Müller
2019-11-11 23:54   ` Thomas Gleixner
2019-11-12  2:25     ` Stephan Müller
2019-11-12 10:16       ` Thomas Gleixner
2019-11-12 22:30   ` kbuild test robot
2019-11-12 23:15     ` Stephan Müller
2019-11-13  0:14   ` kbuild test robot
2019-11-13  0:25     ` Stephan Müller
2019-11-24  4:51   ` Sandy Harris
2019-11-24  9:02     ` Stephan Mueller
2019-11-11 18:19 ` [PATCH v24 02/12] LRNG - allocate one SDRNG instance per NUMA node Stephan Müller
2019-11-11 18:20 ` [PATCH v24 03/12] LRNG - /proc interface Stephan Müller
2019-11-11 18:20 ` [PATCH v24 04/12] LRNG - add switchable DRNG support Stephan Müller
2019-11-11 18:21 ` [PATCH v24 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2019-11-11 18:21 ` [PATCH v24 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2019-11-11 18:22 ` [PATCH v24 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2019-11-11 18:23 ` [PATCH v24 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2019-11-11 18:23 ` [PATCH v24 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2019-11-11 18:24 ` [PATCH v24 10/12] LRNG - add TRNG support Stephan Müller
2019-11-11 18:26 ` [PATCH v24 11/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2019-11-12 19:58   ` Alexander E. Patrakov
2019-11-12 23:11     ` Stephan Müller
2019-11-13  0:36     ` Stephan Müller
2019-11-13  6:02       ` Alexander E. Patrakov
2019-11-14  1:46         ` Stephan Müller
2019-11-11 18:26 ` [PATCH v24 12/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2019-11-12 20:55   ` kbuild test robot
2019-11-12 23:13     ` Stephan Müller
2019-11-12 13:23 ` [PATCH v24 00/12] /dev/random - a new approach with full SP800-90B compliance Florian Weimer
2019-11-12 22:43   ` Stephan Müller
2019-11-12 15:33 ` Andy Lutomirski
2019-11-12 23:03   ` Stephan Müller
2019-11-12 23:26     ` Stephan Müller
2019-11-13  4:24   ` Stephan Müller
2019-11-13  4:48     ` Andy Lutomirski
2019-11-13 12:16       ` Stephan Müller
2019-11-16  9:32 ` [PATCH v25 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2019-11-16  9:33   ` [PATCH v25 01/12] Linux Random Number Generator Stephan Müller
2019-11-16 11:25     ` Thomas Gleixner
2019-11-17 10:30       ` Stephan Müller
2019-11-16 18:13     ` Nicolai Stange
2019-11-17 11:01       ` Stephan Müller
2019-11-16  9:33   ` [PATCH v25 02/12] LRNG - allocate one SDRNG instance per NUMA node Stephan Müller
2019-11-16  9:34   ` [PATCH v25 03/12] LRNG - /proc interface Stephan Müller
2019-11-16 16:39     ` Andy Lutomirski
2019-11-17 12:16       ` Stephan Müller
2019-11-19 10:06         ` Andy Lutomirski
2019-11-19 10:55           ` Stephan Mueller
2019-11-19 17:40             ` Andy Lutomirski
2019-11-16 23:36     ` ebiederm
2019-11-17 11:37       ` Stephan Müller
2019-11-16  9:34   ` [PATCH v25 04/12] LRNG - add switchable DRNG support Stephan Müller
2019-11-16  9:35   ` [PATCH v25 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2019-11-16  9:35   ` [PATCH v25 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2019-11-16  9:35   ` [PATCH v25 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2019-11-16  9:36   ` [PATCH v25 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2019-11-16  9:36   ` [PATCH v25 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2019-11-20 13:33     ` Neil Horman
2019-11-20 20:07       ` Stephan Müller
2019-11-21 14:19         ` Neil Horman
2019-11-21 14:33           ` Stephan Mueller
2019-11-16  9:37   ` [PATCH v25 10/12] LRNG - add TRNG support Stephan Müller
2019-11-16 16:09     ` Andy Lutomirski
2019-11-17 11:10       ` Stephan Müller
2019-11-19 10:07         ` Andy Lutomirski
2019-11-19 10:46           ` Stephan Mueller
2019-11-19 12:41           ` Greg Kroah-Hartman
2019-11-20  8:58             ` Stephan Müller
2019-11-20  9:55               ` Alexander E. Patrakov
2019-11-20 13:29               ` Greg Kroah-Hartman
2019-11-20 19:51                 ` Stephan Müller
2019-11-20 19:57                   ` Alexander E. Patrakov
2019-11-20 20:32                   ` Greg Kroah-Hartman
2019-11-21 13:06                     ` Stephan Müller
2019-11-16  9:37   ` [PATCH v25 11/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2019-11-16  9:38   ` [PATCH v25 12/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2019-11-16 16:51     ` Andy Lutomirski
2019-11-17 22:55       ` Stephan Müller
2019-11-19 10:04         ` Andy Lutomirski
2019-11-19 17:17     ` Randy Dunlap
2019-11-20  9:01       ` Stephan Müller
2019-11-21 12:18     ` Nicolai Stange
2019-11-21 15:18       ` Stephan Müller [this message]
2019-11-23 20:08   ` [PATCH v26 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2019-11-23 20:10     ` [PATCH v26 01/12] Linux Random Number Generator Stephan Müller
2019-11-24 22:44       ` kbuild test robot
2019-11-25  6:29         ` Stephan Mueller
2019-11-23 20:10     ` [PATCH v26 02/12] LRNG - allocate one SDRNG instance per NUMA node Stephan Müller
2019-11-23 20:11     ` [PATCH v26 03/12] LRNG - sysctls and /proc interface Stephan Müller
2019-11-23 20:11     ` [PATCH v26 04/12] LRNG - add switchable DRNG support Stephan Müller
2019-11-23 20:31     ` [PATCH v26 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2019-11-23 20:32     ` [PATCH v26 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2019-11-23 20:32     ` [PATCH v26 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2019-11-23 20:33     ` [PATCH v26 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2019-11-23 20:34     ` [PATCH v26 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2019-11-23 20:34     ` [PATCH v26 10/12] LRNG - add TRNG support Stephan Müller
2019-11-23 20:34     ` [PATCH v26 11/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2019-11-23 20:35     ` [PATCH v26 12/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-09  8:29     ` [PATCH v27 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2020-01-09  8:30       ` [PATCH v27 01/12] Linux Random Number Generator Stephan Müller
2020-01-16  6:09         ` kbuild test robot
2020-01-16  6:41           ` Stephan Mueller
2020-01-09  8:31       ` [PATCH v27 02/12] LRNG - allocate one DRNG instance per NUMA node Stephan Müller
2020-01-09  8:31       ` [PATCH v27 03/12] LRNG - sysctls and /proc interface Stephan Müller
2020-01-09  8:32       ` [PATCH v27 04/12] LRNG - add switchable DRNG support Stephan Müller
2020-01-11  7:09         ` kbuild test robot
2020-01-12 10:12           ` Stephan Müller
2020-01-09  8:32       ` [PATCH v27 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2020-01-09  8:32       ` [PATCH v27 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2020-01-09  8:33       ` [PATCH v27 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2020-01-09  8:33       ` [PATCH v27 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2020-01-09  8:34       ` [PATCH v27 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2020-01-10  0:24         ` Randy Dunlap
2020-01-10  7:45           ` Stephan Mueller
2020-01-09  8:34       ` [PATCH v27 10/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2020-01-10  0:20         ` Randy Dunlap
2020-01-10  8:27           ` Stephan Mueller
2020-01-09  8:35       ` [PATCH v27 11/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-09  8:35       ` [PATCH v27 12/12] LRNG - add power-on and runtime self-tests Stephan Müller
2020-01-10  0:22         ` Randy Dunlap
2020-01-10  7:48           ` Stephan Mueller
2020-01-13 10:39         ` Dan Carpenter
2020-01-13 10:46           ` Stephan Mueller
2020-01-15 10:31       ` [PATCH v28 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2020-01-15 10:31         ` [PATCH v28 01/12] Linux Random Number Generator Stephan Müller
2020-01-16  0:11           ` Randy Dunlap
2020-01-16  7:22             ` Stephan Mueller
2020-01-15 10:32         ` [PATCH v28 02/12] LRNG - allocate one DRNG instance per NUMA node Stephan Müller
2020-01-15 10:32         ` [PATCH v28 03/12] LRNG - sysctls and /proc interface Stephan Müller
2020-01-15 10:32         ` [PATCH v28 04/12] LRNG - add switchable DRNG support Stephan Müller
2020-01-15 10:33         ` [PATCH v28 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2020-01-15 10:33         ` [PATCH v28 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2020-01-16  0:14           ` Randy Dunlap
2020-01-16  6:55             ` Stephan Mueller
2020-01-15 10:34         ` [PATCH v28 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2020-01-16  0:15           ` Randy Dunlap
2020-01-16  6:54             ` Stephan Mueller
2020-01-15 10:34         ` [PATCH v28 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2020-01-15 10:34         ` [PATCH v28 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2020-01-16  0:17           ` Randy Dunlap
2020-01-16  6:51             ` Stephan Mueller
2020-01-15 10:35         ` [PATCH v28 10/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2020-01-15 10:35         ` [PATCH v28 11/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-16  0:18           ` Randy Dunlap
2020-01-16  6:43             ` Stephan Mueller
2020-01-16  6:48               ` Randy Dunlap
2020-01-16  6:52                 ` Stephan Mueller
2020-01-15 10:36         ` [PATCH v28 12/12] LRNG - add power-on and runtime self-tests Stephan Müller
2020-01-19 21:12         ` [PATCH v29 00/12] /dev/random - a new approach with full SP800-90B Stephan Müller
2020-01-19 21:13           ` [PATCH v29 01/12] Linux Random Number Generator Stephan Müller
2020-01-19 21:13           ` [PATCH v29 02/12] LRNG - allocate one DRNG instance per NUMA node Stephan Müller
2020-01-19 21:14           ` [PATCH v29 03/12] LRNG - sysctls and /proc interface Stephan Müller
2020-01-19 21:14           ` [PATCH v29 04/12] LRNG - add switchable DRNG support Stephan Müller
2020-01-19 21:15           ` [PATCH v29 05/12] crypto: DRBG - externalize DRBG functions for LRNG Stephan Müller
2020-01-19 21:16           ` [PATCH v29 06/12] LRNG - add SP800-90A DRBG extension Stephan Müller
2020-01-19 21:16           ` [PATCH v29 07/12] LRNG - add kernel crypto API PRNG extension Stephan Müller
2020-01-19 21:17           ` [PATCH v29 08/12] crypto: provide access to a static Jitter RNG state Stephan Müller
2020-01-19 21:18           ` [PATCH v29 09/12] LRNG - add Jitter RNG fast noise source Stephan Müller
2020-01-19 21:18           ` [PATCH v29 10/12] LRNG - add SP800-90B compliant health tests Stephan Müller
2020-01-19 21:19           ` [PATCH v29 11/12] LRNG - add interface for gathering of raw entropy Stephan Müller
2020-01-19 21:20           ` [PATCH v29 12/12] LRNG - add power-on and runtime self-tests Stephan Müller

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