crypto: remove CONFIG_CRYPTO_STATS

Remove support for the "Crypto usage statistics" feature
(CONFIG_CRYPTO_STATS).  This feature does not appear to have ever been
used, and it is harmful because it significantly reduces performance and
is a large maintenance burden.

Covering each of these points in detail:

1. Feature is not being used

Since these generic crypto statistics are only readable using netlink,
it's fairly straightforward to look for programs that use them.  I'm
unable to find any evidence that any such programs exist.  For example,
Debian Code Search returns no hits except the kernel header and kernel
code itself and translations of the kernel header:
https://codesearch.debian.net/search?q=CRYPTOCFGA_STAT&literal=1&perpkg=1

The patch series that added this feature in 2018
(https://lore.kernel.org/linux-crypto/1537351855-16618-1-git-send-email-clabbe@baylibre.com/)
said "The goal is to have an ifconfig for crypto device."  This doesn't
appear to have happened.

It's not clear that there is real demand for crypto statistics.  Just
because the kernel provides other types of statistics such as I/O and
networking statistics and some people find those useful does not mean
that crypto statistics are useful too.

Further evidence that programs are not using CONFIG_CRYPTO_STATS is that
it was able to be disabled in RHEL and Fedora as a bug fix
(https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/2947).

Even further evidence comes from the fact that there are and have been
bugs in how the stats work, but they were never reported.  For example,
before Linux v6.7 hash stats were double-counted in most cases.

There has also never been any documentation for this feature, so it
might be hard to use even if someone wanted to.

2. CONFIG_CRYPTO_STATS significantly reduces performance

Enabling CONFIG_CRYPTO_STATS significantly reduces the performance of
the crypto API, even if no program ever retrieves the statistics.  This
primarily affects systems with a large number of CPUs.  For example,
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039576 reported
that Lustre client encryption performance improved from 21.7GB/s to
48.2GB/s by disabling CONFIG_CRYPTO_STATS.

It can be argued that this means that CONFIG_CRYPTO_STATS should be
optimized with per-cpu counters similar to many of the networking
counters.  But no one has done this in 5+ years.  This is consistent
with the fact that the feature appears to be unused, so there seems to
be little interest in improving it as opposed to just disabling it.

It can be argued that because CONFIG_CRYPTO_STATS is off by default,
performance doesn't matter.  But Linux distros tend to error on the side
of enabling options.  The option is enabled in Ubuntu and Arch Linux,
and until recently was enabled in RHEL and Fedora (see above).  So, even
just having the option available is harmful to users.

3. CONFIG_CRYPTO_STATS is a large maintenance burden

There are over 1000 lines of code associated with CONFIG_CRYPTO_STATS,
spread among 32 files.  It significantly complicates much of the
implementation of the crypto API.  After the initial submission, many
fixes and refactorings have consumed effort of multiple people to keep
this feature "working".  We should be spending this effort elsewhere.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 522 insertions, 0 deletions

diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
new file mode 100644
index 000000000000..6c571834e86a
--- /dev/null
+++ b/crypto/crypto_user.c
@@ -0,0 +1,522 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Crypto user configuration API.
+ *
+ * Copyright (C) 2011 secunet Security Networks AG
+ * Copyright (C) 2011 Steffen Klassert <steffen.klassert@secunet.com>
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/cryptouser.h>
+#include <linux/sched.h>
+#include <linux/security.h>
+#include <net/netlink.h>
+#include <net/net_namespace.h>
+#include <net/sock.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/internal/rng.h>
+#include <crypto/akcipher.h>
+#include <crypto/kpp.h>
+
+#include "internal.h"
+
+#define null_terminated(x)	(strnlen(x, sizeof(x)) < sizeof(x))
+
+static DEFINE_MUTEX(crypto_cfg_mutex);
+
+struct crypto_dump_info {
+	struct sk_buff *in_skb;
+	struct sk_buff *out_skb;
+	u32 nlmsg_seq;
+	u16 nlmsg_flags;
+};
+
+static struct crypto_alg *crypto_alg_match(struct crypto_user_alg *p, int exact)
+{
+	struct crypto_alg *q, *alg = NULL;
+
+	down_read(&crypto_alg_sem);
+
+	list_for_each_entry(q, &crypto_alg_list, cra_list) {
+		int match = 0;
+
+		if (crypto_is_larval(q))
+			continue;
+
+		if ((q->cra_flags ^ p->cru_type) & p->cru_mask)
+			continue;
+
+		if (strlen(p->cru_driver_name))
+			match = !strcmp(q->cra_driver_name,
+					p->cru_driver_name);
+		else if (!exact)
+			match = !strcmp(q->cra_name, p->cru_name);
+
+		if (!match)
+			continue;
+
+		if (unlikely(!crypto_mod_get(q)))
+			continue;
+
+		alg = q;
+		break;
+	}
+
+	up_read(&crypto_alg_sem);
+
+	return alg;
+}
+
+static int crypto_report_cipher(struct sk_buff *skb, struct crypto_alg *alg)
+{
+	struct crypto_report_cipher rcipher;
+
+	memset(&rcipher, 0, sizeof(rcipher));
+
+	strscpy(rcipher.type, "cipher", sizeof(rcipher.type));
+
+	rcipher.blocksize = alg->cra_blocksize;
+	rcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
+	rcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
+
+	return nla_put(skb, CRYPTOCFGA_REPORT_CIPHER,
+		       sizeof(rcipher), &rcipher);
+}
+
+static int crypto_report_comp(struct sk_buff *skb, struct crypto_alg *alg)
+{
+	struct crypto_report_comp rcomp;
+
+	memset(&rcomp, 0, sizeof(rcomp));
+
+	strscpy(rcomp.type, "compression", sizeof(rcomp.type));
+
+	return nla_put(skb, CRYPTOCFGA_REPORT_COMPRESS, sizeof(rcomp), &rcomp);
+}
+
+static int crypto_report_one(struct crypto_alg *alg,
+			     struct crypto_user_alg *ualg, struct sk_buff *skb)
+{
+	memset(ualg, 0, sizeof(*ualg));
+
+	strscpy(ualg->cru_name, alg->cra_name, sizeof(ualg->cru_name));
+	strscpy(ualg->cru_driver_name, alg->cra_driver_name,
+		sizeof(ualg->cru_driver_name));
+	strscpy(ualg->cru_module_name, module_name(alg->cra_module),
+		sizeof(ualg->cru_module_name));
+
+	ualg->cru_type = 0;
+	ualg->cru_mask = 0;
+	ualg->cru_flags = alg->cra_flags;
+	ualg->cru_refcnt = refcount_read(&alg->cra_refcnt);
+
+	if (nla_put_u32(skb, CRYPTOCFGA_PRIORITY_VAL, alg->cra_priority))
+		goto nla_put_failure;
+	if (alg->cra_flags & CRYPTO_ALG_LARVAL) {
+		struct crypto_report_larval rl;
+
+		memset(&rl, 0, sizeof(rl));
+		strscpy(rl.type, "larval", sizeof(rl.type));
+		if (nla_put(skb, CRYPTOCFGA_REPORT_LARVAL, sizeof(rl), &rl))
+			goto nla_put_failure;
+		goto out;
+	}
+
+	if (alg->cra_type && alg->cra_type->report) {
+		if (alg->cra_type->report(skb, alg))
+			goto nla_put_failure;
+
+		goto out;
+	}
+
+	switch (alg->cra_flags & (CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_LARVAL)) {
+	case CRYPTO_ALG_TYPE_CIPHER:
+		if (crypto_report_cipher(skb, alg))
+			goto nla_put_failure;
+
+		break;
+	case CRYPTO_ALG_TYPE_COMPRESS:
+		if (crypto_report_comp(skb, alg))
+			goto nla_put_failure;
+
+		break;
+	}
+
+out:
+	return 0;
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
+static int crypto_report_alg(struct crypto_alg *alg,
+			     struct crypto_dump_info *info)
+{
+	struct sk_buff *in_skb = info->in_skb;
+	struct sk_buff *skb = info->out_skb;
+	struct nlmsghdr *nlh;
+	struct crypto_user_alg *ualg;
+	int err = 0;
+
+	nlh = nlmsg_put(skb, NETLINK_CB(in_skb).portid, info->nlmsg_seq,
+			CRYPTO_MSG_GETALG, sizeof(*ualg), info->nlmsg_flags);
+	if (!nlh) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	ualg = nlmsg_data(nlh);
+
+	err = crypto_report_one(alg, ualg, skb);
+	if (err) {
+		nlmsg_cancel(skb, nlh);
+		goto out;
+	}
+
+	nlmsg_end(skb, nlh);
+
+out:
+	return err;
+}
+
+static int crypto_report(struct sk_buff *in_skb, struct nlmsghdr *in_nlh,
+			 struct nlattr **attrs)
+{
+	struct net *net = sock_net(in_skb->sk);
+	struct crypto_user_alg *p = nlmsg_data(in_nlh);
+	struct crypto_alg *alg;
+	struct sk_buff *skb;
+	struct crypto_dump_info info;
+	int err;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, 0);
+	if (!alg)
+		return -ENOENT;
+
+	err = -ENOMEM;
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!skb)
+		goto drop_alg;
+
+	info.in_skb = in_skb;
+	info.out_skb = skb;
+	info.nlmsg_seq = in_nlh->nlmsg_seq;
+	info.nlmsg_flags = 0;
+
+	err = crypto_report_alg(alg, &info);
+
+drop_alg:
+	crypto_mod_put(alg);
+
+	if (err) {
+		kfree_skb(skb);
+		return err;
+	}
+
+	return nlmsg_unicast(net->crypto_nlsk, skb, NETLINK_CB(in_skb).portid);
+}
+
+static int crypto_dump_report(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	const size_t start_pos = cb->args[0];
+	size_t pos = 0;
+	struct crypto_dump_info info;
+	struct crypto_alg *alg;
+	int res;
+
+	info.in_skb = cb->skb;
+	info.out_skb = skb;
+	info.nlmsg_seq = cb->nlh->nlmsg_seq;
+	info.nlmsg_flags = NLM_F_MULTI;
+
+	down_read(&crypto_alg_sem);
+	list_for_each_entry(alg, &crypto_alg_list, cra_list) {
+		if (pos >= start_pos) {
+			res = crypto_report_alg(alg, &info);
+			if (res == -EMSGSIZE)
+				break;
+			if (res)
+				goto out;
+		}
+		pos++;
+	}
+	cb->args[0] = pos;
+	res = skb->len;
+out:
+	up_read(&crypto_alg_sem);
+	return res;
+}
+
+static int crypto_dump_report_done(struct netlink_callback *cb)
+{
+	return 0;
+}
+
+static int crypto_update_alg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			     struct nlattr **attrs)
+{
+	struct crypto_alg *alg;
+	struct crypto_user_alg *p = nlmsg_data(nlh);
+	struct nlattr *priority = attrs[CRYPTOCFGA_PRIORITY_VAL];
+	LIST_HEAD(list);
+
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	if (priority && !strlen(p->cru_driver_name))
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, 1);
+	if (!alg)
+		return -ENOENT;
+
+	down_write(&crypto_alg_sem);
+
+	crypto_remove_spawns(alg, &list, NULL);
+
+	if (priority)
+		alg->cra_priority = nla_get_u32(priority);
+
+	up_write(&crypto_alg_sem);
+
+	crypto_mod_put(alg);
+	crypto_remove_final(&list);
+
+	return 0;
+}
+
+static int crypto_del_alg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct nlattr **attrs)
+{
+	struct crypto_alg *alg;
+	struct crypto_user_alg *p = nlmsg_data(nlh);
+	int err;
+
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, 1);
+	if (!alg)
+		return -ENOENT;
+
+	/* We can not unregister core algorithms such as aes-generic.
+	 * We would loose the reference in the crypto_alg_list to this algorithm
+	 * if we try to unregister. Unregistering such an algorithm without
+	 * removing the module is not possible, so we restrict to crypto
+	 * instances that are build from templates. */
+	err = -EINVAL;
+	if (!(alg->cra_flags & CRYPTO_ALG_INSTANCE))
+		goto drop_alg;
+
+	err = -EBUSY;
+	if (refcount_read(&alg->cra_refcnt) > 2)
+		goto drop_alg;
+
+	crypto_unregister_instance((struct crypto_instance *)alg);
+	err = 0;
+
+drop_alg:
+	crypto_mod_put(alg);
+	return err;
+}
+
+static int crypto_add_alg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct nlattr **attrs)
+{
+	int exact = 0;
+	const char *name;
+	struct crypto_alg *alg;
+	struct crypto_user_alg *p = nlmsg_data(nlh);
+	struct nlattr *priority = attrs[CRYPTOCFGA_PRIORITY_VAL];
+
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	if (strlen(p->cru_driver_name))
+		exact = 1;
+
+	if (priority && !exact)
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, exact);
+	if (alg) {
+		crypto_mod_put(alg);
+		return -EEXIST;
+	}
+
+	if (strlen(p->cru_driver_name))
+		name = p->cru_driver_name;
+	else
+		name = p->cru_name;
+
+	alg = crypto_alg_mod_lookup(name, p->cru_type, p->cru_mask);
+	if (IS_ERR(alg))
+		return PTR_ERR(alg);
+
+	down_write(&crypto_alg_sem);
+
+	if (priority)
+		alg->cra_priority = nla_get_u32(priority);
+
+	up_write(&crypto_alg_sem);
+
+	crypto_mod_put(alg);
+
+	return 0;
+}
+
+static int crypto_del_rng(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct nlattr **attrs)
+{
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+	return crypto_del_default_rng();
+}
+
+static int crypto_reportstat(struct sk_buff *in_skb, struct nlmsghdr *in_nlh,
+			     struct nlattr **attrs)
+{
+	/* No longer supported */
+	return -ENOTSUPP;
+}
+
+#define MSGSIZE(type) sizeof(struct type)
+
+static const int crypto_msg_min[CRYPTO_NR_MSGTYPES] = {
+	[CRYPTO_MSG_NEWALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_DELALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_UPDATEALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_GETALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_DELRNG	- CRYPTO_MSG_BASE] = 0,
+	[CRYPTO_MSG_GETSTAT	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+};
+
+static const struct nla_policy crypto_policy[CRYPTOCFGA_MAX+1] = {
+	[CRYPTOCFGA_PRIORITY_VAL]   = { .type = NLA_U32},
+};
+
+#undef MSGSIZE
+
+static const struct crypto_link {
+	int (*doit)(struct sk_buff *, struct nlmsghdr *, struct nlattr **);
+	int (*dump)(struct sk_buff *, struct netlink_callback *);
+	int (*done)(struct netlink_callback *);
+} crypto_dispatch[CRYPTO_NR_MSGTYPES] = {
+	[CRYPTO_MSG_NEWALG	- CRYPTO_MSG_BASE] = { .doit = crypto_add_alg},
+	[CRYPTO_MSG_DELALG	- CRYPTO_MSG_BASE] = { .doit = crypto_del_alg},
+	[CRYPTO_MSG_UPDATEALG	- CRYPTO_MSG_BASE] = { .doit = crypto_update_alg},
+	[CRYPTO_MSG_GETALG	- CRYPTO_MSG_BASE] = { .doit = crypto_report,
+						       .dump = crypto_dump_report,
+						       .done = crypto_dump_report_done},
+	[CRYPTO_MSG_DELRNG	- CRYPTO_MSG_BASE] = { .doit = crypto_del_rng },
+	[CRYPTO_MSG_GETSTAT	- CRYPTO_MSG_BASE] = { .doit = crypto_reportstat},
+};
+
+static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			       struct netlink_ext_ack *extack)
+{
+	struct net *net = sock_net(skb->sk);
+	struct nlattr *attrs[CRYPTOCFGA_MAX+1];
+	const struct crypto_link *link;
+	int type, err;
+
+	type = nlh->nlmsg_type;
+	if (type > CRYPTO_MSG_MAX)
+		return -EINVAL;
+
+	type -= CRYPTO_MSG_BASE;
+	link = &crypto_dispatch[type];
+
+	if ((type == (CRYPTO_MSG_GETALG - CRYPTO_MSG_BASE) &&
+	    (nlh->nlmsg_flags & NLM_F_DUMP))) {
+		struct crypto_alg *alg;
+		unsigned long dump_alloc = 0;
+
+		if (link->dump == NULL)
+			return -EINVAL;
+
+		down_read(&crypto_alg_sem);
+		list_for_each_entry(alg, &crypto_alg_list, cra_list)
+			dump_alloc += CRYPTO_REPORT_MAXSIZE;
+		up_read(&crypto_alg_sem);
+
+		{
+			struct netlink_dump_control c = {
+				.dump = link->dump,
+				.done = link->done,
+				.min_dump_alloc = min(dump_alloc, 65535UL),
+			};
+			err = netlink_dump_start(net->crypto_nlsk, skb, nlh, &c);
+		}
+
+		return err;
+	}
+
+	err = nlmsg_parse_deprecated(nlh, crypto_msg_min[type], attrs,
+				     CRYPTOCFGA_MAX, crypto_policy, extack);
+	if (err < 0)
+		return err;
+
+	if (link->doit == NULL)
+		return -EINVAL;
+
+	return link->doit(skb, nlh, attrs);
+}
+
+static void crypto_netlink_rcv(struct sk_buff *skb)
+{
+	mutex_lock(&crypto_cfg_mutex);
+	netlink_rcv_skb(skb, &crypto_user_rcv_msg);
+	mutex_unlock(&crypto_cfg_mutex);
+}
+
+static int __net_init crypto_netlink_init(struct net *net)
+{
+	struct netlink_kernel_cfg cfg = {
+		.input	= crypto_netlink_rcv,
+	};
+
+	net->crypto_nlsk = netlink_kernel_create(net, NETLINK_CRYPTO, &cfg);
+	return net->crypto_nlsk == NULL ? -ENOMEM : 0;
+}
+
+static void __net_exit crypto_netlink_exit(struct net *net)
+{
+	netlink_kernel_release(net->crypto_nlsk);
+	net->crypto_nlsk = NULL;
+}
+
+static struct pernet_operations crypto_netlink_net_ops = {
+	.init = crypto_netlink_init,
+	.exit = crypto_netlink_exit,
+};
+
+static int __init crypto_user_init(void)
+{
+	return register_pernet_subsys(&crypto_netlink_net_ops);
+}
+
+static void __exit crypto_user_exit(void)
+{
+	unregister_pernet_subsys(&crypto_netlink_net_ops);
+}
+
+module_init(crypto_user_init);
+module_exit(crypto_user_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
+MODULE_DESCRIPTION("Crypto userspace configuration API");
+MODULE_ALIAS("net-pf-16-proto-21");