[PATCH v3 1/4] crypto: Introduce crypto_pool

Dmitry Safonov
2023-01-16T20:15:25Z

Introduce a per-CPU pool of async crypto requests that can be used
in bh-disabled contexts (designed with net RX/TX softirqs as users in
mind). Allocation can sleep and is a slow-path.
Initial implementation has only ahash as a backend and a fix-sized array
of possible algorithms used in parallel.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
crypto/Kconfig | 3 +
crypto/Makefile | 1 +
crypto/crypto_pool.c | 334 ++++++++++++++++++++++++++++++++++++++++++
include/crypto/pool.h | 46 ++++++
4 files changed, 384 insertions(+)
create mode 100644 crypto/crypto_pool.c
create mode 100644 include/crypto/pool.h

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 9c86f7045157..7096654419cb 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1388,6 +1388,9 @@ endmenu
config CRYPTO_HASH_INFO
bool

+config CRYPTO_POOL
+ tristate
+
if !KMSAN # avoid false positives from assembly
if ARM
source "arch/arm/crypto/Kconfig"
diff --git a/crypto/Makefile b/crypto/Makefile
index d0126c915834..eed8f61bc93b 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -63,6 +63,7 @@ obj-$(CONFIG_CRYPTO_ACOMP2) += crypto_acompress.o
cryptomgr-y := algboss.o testmgr.o

obj-$(CONFIG_CRYPTO_MANAGER2) += cryptomgr.o
+obj-$(CONFIG_CRYPTO_POOL) += crypto_pool.o
obj-$(CONFIG_CRYPTO_USER) += crypto_user.o
crypto_user-y := crypto_user_base.o
crypto_user-$(CONFIG_CRYPTO_STATS) += crypto_user_stat.o
diff --git a/crypto/crypto_pool.c b/crypto/crypto_pool.c
new file mode 100644
index 000000000000..17dc2dd482c9
--- /dev/null
+++ b/crypto/crypto_pool.c
@@ -0,0 +1,334 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <crypto/pool.h>
+#include <linux/cpu.h>
+#include <linux/kref.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/percpu.h>
+#include <linux/workqueue.h>
+
+static unsigned long __scratch_size;
+static DEFINE_PER_CPU(void __rcu *, crypto_pool_scratch);
+
+struct crypto_pool_entry {
+ struct ahash_request * __percpu *req;
+ const char *alg;
+ struct kref kref;
+ bool needs_key;
+};
+
+#define CPOOL_SIZE (PAGE_SIZE/sizeof(struct crypto_pool_entry))
+static struct crypto_pool_entry cpool[CPOOL_SIZE];
+static unsigned int cpool_populated;
+static DEFINE_MUTEX(cpool_mutex);
+
+/* Slow-path */
+struct scratches_to_free {
+ struct rcu_head rcu;
+ unsigned int cnt;
+ void *scratches[];
+};
+static void free_old_scratches(struct rcu_head *head)
+{
+ struct scratches_to_free *stf;
+
+ stf = container_of(head, struct scratches_to_free, rcu);
+ while (stf->cnt--)
+ kfree(stf->scratches[stf->cnt]);
+ kfree(stf);
+}
+/*
+ * crypto_pool_reserve_scratch - re-allocates scratch buffer, slow-path
+ * @size: request size for the scratch/temp buffer
+ */
+static int crypto_pool_reserve_scratch(size_t size)
+{
+ struct scratches_to_free *stf;
+ size_t stf_sz = struct_size(stf, scratches, num_possible_cpus());
+ int cpu, err = 0;
+
+ lockdep_assert_held(&cpool_mutex);
+ if (__scratch_size >= size)
+ return 0;
+
+ stf = kmalloc(stf_sz, GFP_KERNEL);
+ if (!stf)
+ return -ENOMEM;
+ stf->cnt = 0;
+
+ size = max(size, __scratch_size);
+ cpus_read_lock();
+ for_each_possible_cpu(cpu) {
+ void *scratch, *old_scratch;
+
+ scratch = kmalloc_node(size, GFP_KERNEL, cpu_to_node(cpu));
+ if (!scratch) {
+ err = -ENOMEM;
+ break;
+ }
+
+ old_scratch = rcu_replace_pointer(per_cpu(crypto_pool_scratch, cpu), scratch, lockdep_is_held(&cpool_mutex));
+ if (!cpu_online(cpu) || !old_scratch) {
+ kfree(old_scratch);
+ continue;
+ }
+ stf->scratches[stf->cnt++] = old_scratch;
+ }
+ cpus_read_unlock();
+ if (!err)
+ __scratch_size = size;
+
+ call_rcu(&stf->rcu, free_old_scratches);
+ return err;
+}
+
+static void crypto_pool_scratch_free(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ kfree(rcu_replace_pointer(per_cpu(crypto_pool_scratch, cpu),
+ NULL, lockdep_is_held(&cpool_mutex)));
+ __scratch_size = 0;
+}
+
+static int __cpool_alloc_ahash(struct crypto_pool_entry *e, const char *alg)
+{
+ struct crypto_ahash *hash, *cpu0_hash;
+ int cpu, ret = -ENOMEM;
+
+ e->alg = kstrdup(alg, GFP_KERNEL);
+ if (!e->alg)
+ return -ENOMEM;
+
+ e->req = alloc_percpu(struct ahash_request *);
+ if (!e->req)
+ goto out_free_alg;
+
+ cpu0_hash = crypto_alloc_ahash(alg, 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(cpu0_hash)) {
+ ret = PTR_ERR(cpu0_hash);
+ goto out_free_req;
+ }
+
+ /* If hash has .setkey(), allocate ahash per-CPU, not only request */
+ e->needs_key = crypto_ahash_get_flags(cpu0_hash) & CRYPTO_TFM_NEED_KEY;
+
+ hash = cpu0_hash;
+ for_each_possible_cpu(cpu) {
+ struct ahash_request *req;
+
+ /*
+ * If ahash has a key - it has to be allocated per-CPU.
+ * In such case re-use for CPU0 hash that just have been
+ * allocated above.
+ */
+ if (!hash)
+ hash = crypto_alloc_ahash(alg, 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(hash))
+ goto out_free_per_cpu;
+
+ req = ahash_request_alloc(hash, GFP_KERNEL);
+ if (!req)
+ goto out_free_hash;
+
+ ahash_request_set_callback(req, 0, NULL, NULL);
+
+ *per_cpu_ptr(e->req, cpu) = req;
+
+ if (e->needs_key)
+ hash = NULL;
+ }
+ kref_init(&e->kref);
+ return 0;
+
+out_free_hash:
+ if (hash != cpu0_hash)
+ crypto_free_ahash(hash);
+
+out_free_per_cpu:
+ for_each_possible_cpu(cpu) {
+ struct ahash_request *req = *per_cpu_ptr(e->req, cpu);
+ struct crypto_ahash *pcpu_hash;
+
+ if (req == NULL)
+ break;
+ pcpu_hash = crypto_ahash_reqtfm(req);
+ ahash_request_free(req);
+ /* hash per-CPU, e->needs_key == true */
+ if (pcpu_hash != cpu0_hash)
+ crypto_free_ahash(pcpu_hash);
+ }
+
+ crypto_free_ahash(cpu0_hash);
+out_free_req:
+ free_percpu(e->req);
+out_free_alg:
+ kfree(e->alg);
+ e->alg = NULL;
+ return ret;
+}
+
+/**
+ * crypto_pool_alloc_ahash - allocates pool for ahash requests
+ * @alg: name of async hash algorithm
+ * @scratch_size: reserve a crypto_pool::scratch buffer of this size
+ */
+int crypto_pool_alloc_ahash(const char *alg, size_t scratch_size)
+{
+ int i, ret;
+
+ /* slow-path */
+ mutex_lock(&cpool_mutex);
+ ret = crypto_pool_reserve_scratch(scratch_size);
+ if (ret)
+ goto out;
+ for (i = 0; i < cpool_populated; i++) {
+ if (cpool[i].alg && !strcmp(cpool[i].alg, alg)) {
+ if (kref_read(&cpool[i].kref) > 0)
+ kref_get(&cpool[i].kref);
+ else
+ kref_init(&cpool[i].kref);
+ ret = i;
+ goto out;
+ }
+ }
+
+ for (i = 0; i < cpool_populated; i++) {
+ if (!cpool[i].alg)
+ break;
+ }
+ if (i >= CPOOL_SIZE) {
+ ret = -ENOSPC;
+ goto out;
+ }
+
+ ret = __cpool_alloc_ahash(&cpool[i], alg);
+ if (!ret) {
+ ret = i;
+ if (i == cpool_populated)
+ cpool_populated++;
+ }
+out:
+ mutex_unlock(&cpool_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(crypto_pool_alloc_ahash);
+
+static void __cpool_free_entry(struct crypto_pool_entry *e)
+{
+ struct crypto_ahash *hash = NULL;
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ if (*per_cpu_ptr(e->req, cpu) == NULL)
+ continue;
+
+ hash = crypto_ahash_reqtfm(*per_cpu_ptr(e->req, cpu));
+ ahash_request_free(*per_cpu_ptr(e->req, cpu));
+ if (e->needs_key) {
+ crypto_free_ahash(hash);
+ hash = NULL;
+ }
+ }
+ if (hash)
+ crypto_free_ahash(hash);
+ free_percpu(e->req);
+ kfree(e->alg);
+ memset(e, 0, sizeof(*e));
+}
+
+static void cpool_cleanup_work_cb(struct work_struct *work)
+{
+ unsigned int i;
+ bool free_scratch = true;
+
+ mutex_lock(&cpool_mutex);
+ for (i = 0; i < cpool_populated; i++) {
+ if (kref_read(&cpool[i].kref) > 0) {
+ free_scratch = false;
+ continue;
+ }
+ if (!cpool[i].alg)
+ continue;
+ __cpool_free_entry(&cpool[i]);
+ }
+ if (free_scratch)
+ crypto_pool_scratch_free();
+ mutex_unlock(&cpool_mutex);
+}
+
+static DECLARE_WORK(cpool_cleanup_work, cpool_cleanup_work_cb);
+static void cpool_schedule_cleanup(struct kref *kref)
+{
+ schedule_work(&cpool_cleanup_work);
+}
+
+/**
+ * crypto_pool_release - decreases number of users for a pool. If it was
+ * the last user of the pool, releases any memory that was consumed.
+ * @id: crypto_pool that was previously allocated by crypto_pool_alloc_ahash()
+ */
+void crypto_pool_release(unsigned int id)
+{
+ if (WARN_ON_ONCE(id > cpool_populated || !cpool[id].alg))
+ return;
+
+ /* slow-path */
+ kref_put(&cpool[id].kref, cpool_schedule_cleanup);
+}
+EXPORT_SYMBOL_GPL(crypto_pool_release);
+
+/**
+ * crypto_pool_get - increases number of users (refcounter) for a pool
+ * @id: crypto_pool that was previously allocated by crypto_pool_alloc_ahash()
+ */
+void crypto_pool_get(unsigned int id)
+{
+ if (WARN_ON_ONCE(id > cpool_populated || !cpool[id].alg))
+ return;
+ kref_get(&cpool[id].kref);
+}
+EXPORT_SYMBOL_GPL(crypto_pool_get);
+
+int crypto_pool_start(unsigned int id, struct crypto_pool *c)
+{
+ struct crypto_pool_ahash *ret = (struct crypto_pool_ahash *)c;
+
+ rcu_read_lock_bh();
+ if (WARN_ON_ONCE(id > cpool_populated || !cpool[id].alg)) {
+ rcu_read_unlock_bh();
+ return -EINVAL;
+ }
+ ret->req = *this_cpu_ptr(cpool[id].req);
+ /*
+ * Pairs with crypto_pool_reserve_scratch(), scratch area is
+ * valid (allocated) until crypto_pool_end().
+ */
+ ret->base.scratch = rcu_dereference_bh(*this_cpu_ptr(&crypto_pool_scratch));
+ return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_pool_start);
+
+/**
+ * crypto_pool_algo - return algorithm of crypto_pool
+ * @id: crypto_pool that was previously allocated by crypto_pool_alloc_ahash()
+ * @buf: buffer to return name of algorithm
+ * @buf_len: size of @buf
+ */
+size_t crypto_pool_algo(unsigned int id, char *buf, size_t buf_len)
+{
+ size_t ret = 0;
+
+ /* slow-path */
+ mutex_lock(&cpool_mutex);
+ if (cpool[id].alg)
+ ret = strscpy(buf, cpool[id].alg, buf_len);
+ mutex_unlock(&cpool_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(crypto_pool_algo);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Per-CPU pool of crypto requests");
diff --git a/include/crypto/pool.h b/include/crypto/pool.h
new file mode 100644
index 000000000000..e266c1cba7de
--- /dev/null
+++ b/include/crypto/pool.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _CRYPTO_POOL_H
+#define _CRYPTO_POOL_H
+
+#include <crypto/hash.h>
+
+/**
+ * struct crypto_pool - generic type for different crypto requests
+ * @scratch: per-CPU temporary area, that can be used between
+ * crypto_pool_start() and crypto_pool_end() to perform
+ * crypto requests
+ */
+struct crypto_pool {
+ void *scratch;
+};
+
+/**
+ * struct crypto_pool_ahash - per-CPU pool of ahash_requests
+ * @base: common members that can be used by any async crypto ops
+ * @req: pre-allocated ahash request
+ */
+struct crypto_pool_ahash {
+ struct crypto_pool base;
+ struct ahash_request *req;
+};
+
+int crypto_pool_alloc_ahash(const char *alg, size_t scratch_size);
+void crypto_pool_get(unsigned int id);
+void crypto_pool_release(unsigned int id);
+
+/**
+ * crypto_pool_start - disable bh and start using crypto_pool
+ * @id: crypto_pool that was previously allocated by crypto_pool_alloc_ahash()
+ * @c: returned crypto_pool for usage (uninitialized on failure)
+ */
+int crypto_pool_start(unsigned int id, struct crypto_pool *c);
+/**
+ * crypto_pool_end - enable bh and stop using crypto_pool
+ */
+static inline void crypto_pool_end(void)
+{
+ rcu_read_unlock_bh();
+}
+size_t crypto_pool_algo(unsigned int id, char *buf, size_t buf_len);
+
+#endif /* _CRYPTO_POOL_H */
--
2.39.0