[PATCH net-next v2 5/5] net/tcp: Remove tcp_sigpool

Eric Biggers
2026-04-27T17:27:53Z

tcp_sigpool is no longer used. It existed only as a workaround for
issues in the design of the crypto_ahash API, which have been avoided by
switching to the much easier-to-use library APIs instead. Remove it.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
include/net/tcp.h | 34 ----
net/ipv4/Kconfig | 3 -
net/ipv4/Makefile | 1 -
net/ipv4/tcp_sigpool.c | 366 -----------------------------------------
4 files changed, 404 deletions(-)
delete mode 100644 net/ipv4/tcp_sigpool.c

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 8817e7b8cc67..660ad8c63395 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2015,44 +2015,10 @@ struct tcp6_pseudohdr {
struct in6_addr daddr;
__be32 len;
__be32 protocol; /* including padding */
};

-/*
- * struct tcp_sigpool - per-CPU pool of ahash_requests
- * @scratch: per-CPU temporary area, that can be used between
- * tcp_sigpool_start() and tcp_sigpool_end() to perform
- * crypto request
- * @req: pre-allocated ahash request
- */
-struct tcp_sigpool {
- void *scratch;
- struct ahash_request *req;
-};
-
-int tcp_sigpool_alloc_ahash(const char *alg, size_t scratch_size);
-void tcp_sigpool_get(unsigned int id);
-void tcp_sigpool_release(unsigned int id);
-int tcp_sigpool_hash_skb_data(struct tcp_sigpool *hp,
- const struct sk_buff *skb,
- unsigned int header_len);
-
-/**
- * tcp_sigpool_start - disable bh and start using tcp_sigpool_ahash
- * @id: tcp_sigpool that was previously allocated by tcp_sigpool_alloc_ahash()
- * @c: returned tcp_sigpool for usage (uninitialized on failure)
- *
- * Returns: 0 on success, error otherwise.
- */
-int tcp_sigpool_start(unsigned int id, struct tcp_sigpool *c);
-/**
- * tcp_sigpool_end - enable bh and stop using tcp_sigpool
- * @c: tcp_sigpool context that was returned by tcp_sigpool_start()
- */
-void tcp_sigpool_end(struct tcp_sigpool *c);
-size_t tcp_sigpool_algo(unsigned int id, char *buf, size_t buf_len);
-/* - functions */
void tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
const struct sock *sk, const struct sk_buff *skb);
int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
int family, u8 prefixlen, int l3index, u8 flags,
const u8 *newkey, u8 newkeylen);
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 77b053b445a0..301b47660305 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -739,13 +739,10 @@ config DEFAULT_TCP_CONG
default "dctcp" if DEFAULT_DCTCP
default "cdg" if DEFAULT_CDG
default "bbr" if DEFAULT_BBR
default "cubic"

-config TCP_SIGPOOL
- tristate
-
config TCP_AO
bool "TCP: Authentication Option (RFC5925)"
select CRYPTO_LIB_AES_CBC_MACS
select CRYPTO_LIB_SHA1
select CRYPTO_LIB_SHA256
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 7f9f98813986..7964234f0d08 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -58,11 +58,10 @@ obj-$(CONFIG_TCP_CONG_NV) += tcp_nv.o
obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.o
obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
-obj-$(CONFIG_TCP_SIGPOOL) += tcp_sigpool.o
obj-$(CONFIG_NET_SOCK_MSG) += tcp_bpf.o
obj-$(CONFIG_BPF_SYSCALL) += udp_bpf.o
obj-$(CONFIG_NETLABEL) += cipso_ipv4.o

obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
diff --git a/net/ipv4/tcp_sigpool.c b/net/ipv4/tcp_sigpool.c
deleted file mode 100644
index 10b2e5970c40..000000000000
--- a/net/ipv4/tcp_sigpool.c
+++ /dev/null
@@ -1,366 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-
-#include <crypto/hash.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>
-#include <net/tcp.h>
-
-static size_t __scratch_size;
-struct sigpool_scratch {
- local_lock_t bh_lock;
- void __rcu *pad;
-};
-
-static DEFINE_PER_CPU(struct sigpool_scratch, sigpool_scratch) = {
- .bh_lock = INIT_LOCAL_LOCK(bh_lock),
-};
-
-struct sigpool_entry {
- struct crypto_ahash *hash;
- const char *alg;
- struct kref kref;
- uint16_t needs_key:1,
- reserved:15;
-};
-
-#define CPOOL_SIZE (PAGE_SIZE / sizeof(struct sigpool_entry))
-static struct sigpool_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);
-}
-
-/**
- * sigpool_reserve_scratch - re-allocates scratch buffer, slow-path
- * @size: request size for the scratch/temp buffer
- */
-static int sigpool_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(sigpool_scratch.pad, 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 sigpool_scratch_free(void)
-{
- int cpu;
-
- for_each_possible_cpu(cpu)
- kfree(rcu_replace_pointer(per_cpu(sigpool_scratch.pad, cpu),
- NULL, lockdep_is_held(&cpool_mutex)));
- __scratch_size = 0;
-}
-
-static int __cpool_try_clone(struct crypto_ahash *hash)
-{
- struct crypto_ahash *tmp;
-
- tmp = crypto_clone_ahash(hash);
- if (IS_ERR(tmp))
- return PTR_ERR(tmp);
-
- crypto_free_ahash(tmp);
- return 0;
-}
-
-static int __cpool_alloc_ahash(struct sigpool_entry *e, const char *alg)
-{
- struct crypto_ahash *cpu0_hash;
- int ret;
-
- e->alg = kstrdup(alg, GFP_KERNEL);
- if (!e->alg)
- return -ENOMEM;
-
- cpu0_hash = crypto_alloc_ahash(alg, 0, CRYPTO_ALG_ASYNC);
- if (IS_ERR(cpu0_hash)) {
- ret = PTR_ERR(cpu0_hash);
- goto out_free_alg;
- }
-
- e->needs_key = crypto_ahash_get_flags(cpu0_hash) & CRYPTO_TFM_NEED_KEY;
-
- ret = __cpool_try_clone(cpu0_hash);
- if (ret)
- goto out_free_cpu0_hash;
- e->hash = cpu0_hash;
- kref_init(&e->kref);
- return 0;
-
-out_free_cpu0_hash:
- crypto_free_ahash(cpu0_hash);
-out_free_alg:
- kfree(e->alg);
- e->alg = NULL;
- return ret;
-}
-
-/**
- * tcp_sigpool_alloc_ahash - allocates pool for ahash requests
- * @alg: name of async hash algorithm
- * @scratch_size: reserve a tcp_sigpool::scratch buffer of this size
- */
-int tcp_sigpool_alloc_ahash(const char *alg, size_t scratch_size)
-{
- int i, ret;
-
- /* slow-path */
- mutex_lock(&cpool_mutex);
- ret = sigpool_reserve_scratch(scratch_size);
- if (ret)
- goto out;
- for (i = 0; i < cpool_populated; i++) {
- if (!cpool[i].alg)
- continue;
- if (strcmp(cpool[i].alg, alg))
- continue;
-
- /* pairs with tcp_sigpool_release() */
- if (!kref_get_unless_zero(&cpool[i].kref))
- 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(tcp_sigpool_alloc_ahash);
-
-static void __cpool_free_entry(struct sigpool_entry *e)
-{
- crypto_free_ahash(e->hash);
- kfree(e->alg);
- memset(e, 0, sizeof(*e));
-}
-
-static void cpool_cleanup_work_cb(struct work_struct *work)
-{
- bool free_scratch = true;
- unsigned int i;
-
- 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)
- sigpool_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);
-}
-
-/**
- * tcp_sigpool_release - decreases number of users for a pool. If it was
- * the last user of the pool, releases any memory that was consumed.
- * @id: tcp_sigpool that was previously allocated by tcp_sigpool_alloc_ahash()
- */
-void tcp_sigpool_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(tcp_sigpool_release);
-
-/**
- * tcp_sigpool_get - increases number of users (refcounter) for a pool
- * @id: tcp_sigpool that was previously allocated by tcp_sigpool_alloc_ahash()
- */
-void tcp_sigpool_get(unsigned int id)
-{
- if (WARN_ON_ONCE(id >= cpool_populated || !cpool[id].alg))
- return;
- kref_get(&cpool[id].kref);
-}
-EXPORT_SYMBOL_GPL(tcp_sigpool_get);
-
-int tcp_sigpool_start(unsigned int id, struct tcp_sigpool *c) __cond_acquires(0, RCU_BH)
-{
- struct crypto_ahash *hash;
-
- rcu_read_lock_bh();
- if (WARN_ON_ONCE(id >= cpool_populated || !cpool[id].alg)) {
- rcu_read_unlock_bh();
- return -EINVAL;
- }
-
- hash = crypto_clone_ahash(cpool[id].hash);
- if (IS_ERR(hash)) {
- rcu_read_unlock_bh();
- return PTR_ERR(hash);
- }
-
- c->req = ahash_request_alloc(hash, GFP_ATOMIC);
- if (!c->req) {
- crypto_free_ahash(hash);
- rcu_read_unlock_bh();
- return -ENOMEM;
- }
- ahash_request_set_callback(c->req, 0, NULL, NULL);
-
- /* Pairs with tcp_sigpool_reserve_scratch(), scratch area is
- * valid (allocated) until tcp_sigpool_end().
- */
- local_lock_nested_bh(&sigpool_scratch.bh_lock);
- c->scratch = rcu_dereference_bh(*this_cpu_ptr(&sigpool_scratch.pad));
- return 0;
-}
-EXPORT_SYMBOL_GPL(tcp_sigpool_start);
-
-void tcp_sigpool_end(struct tcp_sigpool *c) __releases(RCU_BH)
-{
- struct crypto_ahash *hash = crypto_ahash_reqtfm(c->req);
-
- local_unlock_nested_bh(&sigpool_scratch.bh_lock);
- rcu_read_unlock_bh();
- ahash_request_free(c->req);
- crypto_free_ahash(hash);
-}
-EXPORT_SYMBOL_GPL(tcp_sigpool_end);
-
-/**
- * tcp_sigpool_algo - return algorithm of tcp_sigpool
- * @id: tcp_sigpool that was previously allocated by tcp_sigpool_alloc_ahash()
- * @buf: buffer to return name of algorithm
- * @buf_len: size of @buf
- */
-size_t tcp_sigpool_algo(unsigned int id, char *buf, size_t buf_len)
-{
- if (WARN_ON_ONCE(id >= cpool_populated || !cpool[id].alg))
- return -EINVAL;
-
- return strscpy(buf, cpool[id].alg, buf_len);
-}
-EXPORT_SYMBOL_GPL(tcp_sigpool_algo);
-
-/**
- * tcp_sigpool_hash_skb_data - hash data in skb with initialized tcp_sigpool
- * @hp: tcp_sigpool pointer
- * @skb: buffer to add sign for
- * @header_len: TCP header length for this segment
- */
-int tcp_sigpool_hash_skb_data(struct tcp_sigpool *hp,
- const struct sk_buff *skb,
- unsigned int header_len)
-{
- const unsigned int head_data_len = skb_headlen(skb) > header_len ?
- skb_headlen(skb) - header_len : 0;
- const struct skb_shared_info *shi = skb_shinfo(skb);
- const struct tcphdr *tp = tcp_hdr(skb);
- struct ahash_request *req = hp->req;
- struct sk_buff *frag_iter;
- struct scatterlist sg;
- unsigned int i;
-
- sg_init_table(&sg, 1);
-
- sg_set_buf(&sg, ((u8 *)tp) + header_len, head_data_len);
- ahash_request_set_crypt(req, &sg, NULL, head_data_len);
- if (crypto_ahash_update(req))
- return 1;
-
- for (i = 0; i < shi->nr_frags; ++i) {
- const skb_frag_t *f = &shi->frags[i];
- unsigned int offset = skb_frag_off(f);
- struct page *page;
-
- page = skb_frag_page(f) + (offset >> PAGE_SHIFT);
- sg_set_page(&sg, page, skb_frag_size(f), offset_in_page(offset));
- ahash_request_set_crypt(req, &sg, NULL, skb_frag_size(f));
- if (crypto_ahash_update(req))
- return 1;
- }
-
- skb_walk_frags(skb, frag_iter)
- if (tcp_sigpool_hash_skb_data(hp, frag_iter, 0))
- return 1;
-
- return 0;
-}
-EXPORT_SYMBOL(tcp_sigpool_hash_skb_data);
-
-MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("Per-CPU pool of crypto requests");
--
2.54.0