Re: [PATCH v9 net-next 01/23] net/tcp: Prepare tcp_md5sig_pool for TCP-AO
From: Eric Dumazet
Date: Tue Aug 08 2023 - 15:22:50 EST
On Wed, Aug 2, 2023 at 7:27 PM Dmitry Safonov <dima@xxxxxxxxxx> wrote:
>
> TCP-AO, similarly to TCP-MD5, needs to allocate tfms on a slow-path,
> which is setsockopt() and use crypto ahash requests on fast paths,
> which are RX/TX softirqs. Also, it needs a temporary/scratch buffer
> for preparing the hash.
>
> Rework tcp_md5sig_pool in order to support other hashing algorithms
> than MD5. It will make it possible to share pre-allocated crypto_ahash
> descriptors and scratch area between all TCP hash users.
>
> Internally tcp_sigpool calls crypto_clone_ahash() API over pre-allocated
> crypto ahash tfm. Kudos to Herbert, who provided this new crypto API.
>
> I was a little concerned over GFP_ATOMIC allocations of ahash and
> crypto_request in RX/TX (see tcp_sigpool_start()), so I benchmarked both
> "backends" with different algorithms, using patched version of iperf3[2].
> On my laptop with i7-7600U @ 2.80GHz:
>
> clone-tfm per-CPU-requests
> TCP-MD5 2.25 Gbits/sec 2.30 Gbits/sec
> TCP-AO(hmac(sha1)) 2.53 Gbits/sec 2.54 Gbits/sec
> TCP-AO(hmac(sha512)) 1.67 Gbits/sec 1.64 Gbits/sec
> TCP-AO(hmac(sha384)) 1.77 Gbits/sec 1.80 Gbits/sec
> TCP-AO(hmac(sha224)) 1.29 Gbits/sec 1.30 Gbits/sec
> TCP-AO(hmac(sha3-512)) 481 Mbits/sec 480 Mbits/sec
> TCP-AO(hmac(md5)) 2.07 Gbits/sec 2.12 Gbits/sec
> TCP-AO(hmac(rmd160)) 1.01 Gbits/sec 995 Mbits/sec
> TCP-AO(cmac(aes128)) [not supporetd yet] 2.11 Gbits/sec
>
> So, it seems that my concerns don't have strong grounds and per-CPU
> crypto_request allocation can be dropped/removed from tcp_sigpool once
> ciphers get crypto_clone_ahash() support.
>
> [1]: https://lore.kernel.org/all/ZDefxOq6Ax0JeTRH@xxxxxxxxxxxxxxxxxxx/T/#u
> [2]: https://github.com/0x7f454c46/iperf/tree/tcp-md5-ao
> Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
> Reviewed-by: Steen Hegelund <Steen.Hegelund@xxxxxxxxxxxxx>
> Acked-by: David Ahern <dsahern@xxxxxxxxxx>
> ---
> include/net/tcp.h | 50 ++++--
> net/ipv4/Kconfig | 4 +
> net/ipv4/Makefile | 1 +
> net/ipv4/tcp.c | 139 +++------------
> net/ipv4/tcp_ipv4.c | 97 ++++++-----
> net/ipv4/tcp_minisocks.c | 21 ++-
> net/ipv4/tcp_sigpool.c | 358 +++++++++++++++++++++++++++++++++++++++
> net/ipv6/tcp_ipv6.c | 60 +++----
> 8 files changed, 519 insertions(+), 211 deletions(-)
> create mode 100644 net/ipv4/tcp_sigpool.c
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 6d77c08d83b7..506138e69643 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -1700,12 +1700,39 @@ union tcp_md5sum_block {
> #endif
> };
>
> -/* - pool: digest algorithm, hash description and scratch buffer */
> -struct tcp_md5sig_pool {
> - struct ahash_request *md5_req;
> - void *scratch;
> +/*
> + * 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 */
> int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
> const struct sock *sk, const struct sk_buff *skb);
> @@ -1761,17 +1788,12 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
> #define tcp_twsk_md5_key(twsk) NULL
> #endif
>
> -bool tcp_alloc_md5sig_pool(void);
> +int tcp_md5_alloc_sigpool(void);
> +void tcp_md5_release_sigpool(void);
> +void tcp_md5_add_sigpool(void);
> +extern int tcp_md5_sigpool_id;
>
> -struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
> -static inline void tcp_put_md5sig_pool(void)
> -{
> - local_bh_enable();
> -}
> -
> -int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
> - unsigned int header_len);
> -int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
> +int tcp_md5_hash_key(struct tcp_sigpool *hp,
> const struct tcp_md5sig_key *key);
>
> /* From tcp_fastopen.c */
> diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
> index 2dfb12230f08..89e2ab023272 100644
> --- a/net/ipv4/Kconfig
> +++ b/net/ipv4/Kconfig
> @@ -741,10 +741,14 @@ config DEFAULT_TCP_CONG
> default "bbr" if DEFAULT_BBR
> default "cubic"
>
> +config TCP_SIGPOOL
> + tristate
> +
> config TCP_MD5SIG
> bool "TCP: MD5 Signature Option support (RFC2385)"
> select CRYPTO
> select CRYPTO_MD5
> + select TCP_SIGPOOL
> help
> RFC2385 specifies a method of giving MD5 protection to TCP sessions.
> Its main (only?) use is to protect BGP sessions between core routers
> diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
> index b18ba8ef93ad..cd760793cfcb 100644
> --- a/net/ipv4/Makefile
> +++ b/net/ipv4/Makefile
> @@ -62,6 +62,7 @@ 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
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index aca5620cf3ba..e91931d0350e 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -4310,141 +4310,46 @@ int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval,
> EXPORT_SYMBOL(tcp_getsockopt);
>
> #ifdef CONFIG_TCP_MD5SIG
> -static DEFINE_PER_CPU(struct tcp_md5sig_pool, tcp_md5sig_pool);
> -static DEFINE_MUTEX(tcp_md5sig_mutex);
> -static bool tcp_md5sig_pool_populated = false;
> +int tcp_md5_sigpool_id = -1;
> +EXPORT_SYMBOL_GPL(tcp_md5_sigpool_id);
>
> -static void __tcp_alloc_md5sig_pool(void)
> +int tcp_md5_alloc_sigpool(void)
> {
> - struct crypto_ahash *hash;
> - int cpu;
> + size_t scratch_size;
> + int ret;
>
> - hash = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
> - if (IS_ERR(hash))
> - return;
> -
> - for_each_possible_cpu(cpu) {
> - void *scratch = per_cpu(tcp_md5sig_pool, cpu).scratch;
> - struct ahash_request *req;
> -
> - if (!scratch) {
> - scratch = kmalloc_node(sizeof(union tcp_md5sum_block) +
> - sizeof(struct tcphdr),
> - GFP_KERNEL,
> - cpu_to_node(cpu));
> - if (!scratch)
> - return;
> - per_cpu(tcp_md5sig_pool, cpu).scratch = scratch;
> - }
> - if (per_cpu(tcp_md5sig_pool, cpu).md5_req)
> - continue;
> -
> - req = ahash_request_alloc(hash, GFP_KERNEL);
> - if (!req)
> - return;
> -
> - ahash_request_set_callback(req, 0, NULL, NULL);
> -
> - per_cpu(tcp_md5sig_pool, cpu).md5_req = req;
> + scratch_size = sizeof(union tcp_md5sum_block) + sizeof(struct tcphdr);
> + ret = tcp_sigpool_alloc_ahash("md5", scratch_size);
> + if (ret >= 0) {
> + tcp_md5_sigpool_id = ret;
tcp_md5_alloc_sigpool() can be called from multiple cpus,
yet you are writing over tcp_md5_sigpool_id here without any
spinlock/mutex/annotations ?
KCSAN would eventually file a report, and a compiler might very well
transform this to
tcp_md5_sigpool_id = random_value;
<window where readers might catch garbage>
tcp_md5_sigpool_id = ret;
> + return 0;
> }
> - /* before setting tcp_md5sig_pool_populated, we must commit all writes
> - * to memory. See smp_rmb() in tcp_get_md5sig_pool()
> - */
> - smp_wmb();
> - /* Paired with READ_ONCE() from tcp_alloc_md5sig_pool()
> - * and tcp_get_md5sig_pool().
> - */
> - WRITE_ONCE(tcp_md5sig_pool_populated, true);
> + return ret;
> }
>
> -bool tcp_alloc_md5sig_pool(void)
> +void tcp_md5_release_sigpool(void)
> {
> - /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */
> - if (unlikely(!READ_ONCE(tcp_md5sig_pool_populated))) {
> - mutex_lock(&tcp_md5sig_mutex);
> -
> - if (!tcp_md5sig_pool_populated)
> - __tcp_alloc_md5sig_pool();
> -
> - mutex_unlock(&tcp_md5sig_mutex);
> - }
> - /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */
> - return READ_ONCE(tcp_md5sig_pool_populated);
> + tcp_sigpool_release(tcp_md5_sigpool_id);
race reading tcp_md5_sigpool_id
> }
> -EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
>
> -
> -/**
> - * tcp_get_md5sig_pool - get md5sig_pool for this user
> - *
> - * We use percpu structure, so if we succeed, we exit with preemption
> - * and BH disabled, to make sure another thread or softirq handling
> - * wont try to get same context.
> - */
> -struct tcp_md5sig_pool *tcp_get_md5sig_pool(void)
> +void tcp_md5_add_sigpool(void)
> {
> - local_bh_disable();
> -
> - /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */
> - if (READ_ONCE(tcp_md5sig_pool_populated)) {
> - /* coupled with smp_wmb() in __tcp_alloc_md5sig_pool() */
> - smp_rmb();
> - return this_cpu_ptr(&tcp_md5sig_pool);
> - }
> - local_bh_enable();
> - return NULL;
> + tcp_sigpool_get(tcp_md5_sigpool_id);
> }
> -EXPORT_SYMBOL(tcp_get_md5sig_pool);
>
> -int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *hp,
> - const struct sk_buff *skb, unsigned int header_len)
> -{
> - struct scatterlist sg;
> - const struct tcphdr *tp = tcp_hdr(skb);
> - struct ahash_request *req = hp->md5_req;
> - unsigned int i;
> - 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);
> - struct sk_buff *frag_iter;
> -
> - 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 = 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_md5_hash_skb_data(hp, frag_iter, 0))
> - return 1;
> -
> - return 0;
> -}
> -EXPORT_SYMBOL(tcp_md5_hash_skb_data);
> -
> -int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct tcp_md5sig_key *key)
> +int tcp_md5_hash_key(struct tcp_sigpool *hp,
> + const struct tcp_md5sig_key *key)
> {
> u8 keylen = READ_ONCE(key->keylen); /* paired with WRITE_ONCE() in tcp_md5_do_add */
> struct scatterlist sg;
>
> sg_init_one(&sg, key->key, keylen);
> - ahash_request_set_crypt(hp->md5_req, &sg, NULL, keylen);
> + ahash_request_set_crypt(hp->req, &sg, NULL, keylen);
>
> - /* We use data_race() because tcp_md5_do_add() might change key->key under us */
> - return data_race(crypto_ahash_update(hp->md5_req));
> + /* We use data_race() because tcp_md5_do_add() might change
> + * key->key under us
> + */
> + return data_race(crypto_ahash_update(hp->req));
> }
> EXPORT_SYMBOL(tcp_md5_hash_key);
>
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 09cffbc82d32..600e49b23fbe 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1220,10 +1220,6 @@ static int __tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
> key = sock_kmalloc(sk, sizeof(*key), gfp | __GFP_ZERO);
> if (!key)
> return -ENOMEM;
> - if (!tcp_alloc_md5sig_pool()) {
> - sock_kfree_s(sk, key, sizeof(*key));
> - return -ENOMEM;
> - }
>
> memcpy(key->key, newkey, newkeylen);
> key->keylen = newkeylen;
> @@ -1245,15 +1241,21 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
> struct tcp_sock *tp = tcp_sk(sk);
>
> if (!rcu_dereference_protected(tp->md5sig_info, lockdep_sock_is_held(sk))) {
> - if (tcp_md5sig_info_add(sk, GFP_KERNEL))
> + if (tcp_md5_alloc_sigpool())
> return -ENOMEM;
>
> + if (tcp_md5sig_info_add(sk, GFP_KERNEL)) {
> + tcp_md5_release_sigpool();
> + return -ENOMEM;
> + }
> +
> if (!static_branch_inc(&tcp_md5_needed.key)) {
> struct tcp_md5sig_info *md5sig;
>
> md5sig = rcu_dereference_protected(tp->md5sig_info, lockdep_sock_is_held(sk));
> rcu_assign_pointer(tp->md5sig_info, NULL);
> kfree_rcu(md5sig, rcu);
> + tcp_md5_release_sigpool();
> return -EUSERS;
> }
> }
> @@ -1270,8 +1272,12 @@ int tcp_md5_key_copy(struct sock *sk, const union tcp_md5_addr *addr,
> struct tcp_sock *tp = tcp_sk(sk);
>
> if (!rcu_dereference_protected(tp->md5sig_info, lockdep_sock_is_held(sk))) {
> - if (tcp_md5sig_info_add(sk, sk_gfp_mask(sk, GFP_ATOMIC)))
> + tcp_md5_add_sigpool();
> +
> + if (tcp_md5sig_info_add(sk, sk_gfp_mask(sk, GFP_ATOMIC))) {
> + tcp_md5_release_sigpool();
> return -ENOMEM;
> + }
>
> if (!static_key_fast_inc_not_disabled(&tcp_md5_needed.key.key)) {
> struct tcp_md5sig_info *md5sig;
> @@ -1280,6 +1286,7 @@ int tcp_md5_key_copy(struct sock *sk, const union tcp_md5_addr *addr,
> net_warn_ratelimited("Too many TCP-MD5 keys in the system\n");
> rcu_assign_pointer(tp->md5sig_info, NULL);
> kfree_rcu(md5sig, rcu);
> + tcp_md5_release_sigpool();
> return -EUSERS;
> }
> }
> @@ -1379,7 +1386,7 @@ static int tcp_v4_parse_md5_keys(struct sock *sk, int optname,
> cmd.tcpm_key, cmd.tcpm_keylen);
> }
>
> -static int tcp_v4_md5_hash_headers(struct tcp_md5sig_pool *hp,
> +static int tcp_v4_md5_hash_headers(struct tcp_sigpool *hp,
> __be32 daddr, __be32 saddr,
> const struct tcphdr *th, int nbytes)
> {
> @@ -1399,38 +1406,35 @@ static int tcp_v4_md5_hash_headers(struct tcp_md5sig_pool *hp,
> _th->check = 0;
>
> sg_init_one(&sg, bp, sizeof(*bp) + sizeof(*th));
> - ahash_request_set_crypt(hp->md5_req, &sg, NULL,
> + ahash_request_set_crypt(hp->req, &sg, NULL,
> sizeof(*bp) + sizeof(*th));
> - return crypto_ahash_update(hp->md5_req);
> + return crypto_ahash_update(hp->req);
> }
>
> static int tcp_v4_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
> __be32 daddr, __be32 saddr, const struct tcphdr *th)
> {
> - struct tcp_md5sig_pool *hp;
> - struct ahash_request *req;
> + struct tcp_sigpool hp;
>
> - hp = tcp_get_md5sig_pool();
> - if (!hp)
> - goto clear_hash_noput;
> - req = hp->md5_req;
> + if (tcp_sigpool_start(tcp_md5_sigpool_id, &hp))
> + goto clear_hash_nostart;
>
> - if (crypto_ahash_init(req))
> + if (crypto_ahash_init(hp.req))
> goto clear_hash;
> - if (tcp_v4_md5_hash_headers(hp, daddr, saddr, th, th->doff << 2))
> + if (tcp_v4_md5_hash_headers(&hp, daddr, saddr, th, th->doff << 2))
> goto clear_hash;
> - if (tcp_md5_hash_key(hp, key))
> + if (tcp_md5_hash_key(&hp, key))
> goto clear_hash;
> - ahash_request_set_crypt(req, NULL, md5_hash, 0);
> - if (crypto_ahash_final(req))
> + ahash_request_set_crypt(hp.req, NULL, md5_hash, 0);
> + if (crypto_ahash_final(hp.req))
> goto clear_hash;
>
> - tcp_put_md5sig_pool();
> + tcp_sigpool_end(&hp);
> return 0;
>
> clear_hash:
> - tcp_put_md5sig_pool();
> -clear_hash_noput:
> + tcp_sigpool_end(&hp);
> +clear_hash_nostart:
> memset(md5_hash, 0, 16);
> return 1;
> }
> @@ -1439,9 +1443,8 @@ int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
> const struct sock *sk,
> const struct sk_buff *skb)
> {
> - struct tcp_md5sig_pool *hp;
> - struct ahash_request *req;
> const struct tcphdr *th = tcp_hdr(skb);
> + struct tcp_sigpool hp;
> __be32 saddr, daddr;
>
> if (sk) { /* valid for establish/request sockets */
> @@ -1453,30 +1456,28 @@ int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
> daddr = iph->daddr;
> }
>
> - hp = tcp_get_md5sig_pool();
> - if (!hp)
> - goto clear_hash_noput;
> - req = hp->md5_req;
> + if (tcp_sigpool_start(tcp_md5_sigpool_id, &hp))
> + goto clear_hash_nostart;
>
> - if (crypto_ahash_init(req))
> + if (crypto_ahash_init(hp.req))
> goto clear_hash;
>
> - if (tcp_v4_md5_hash_headers(hp, daddr, saddr, th, skb->len))
> + if (tcp_v4_md5_hash_headers(&hp, daddr, saddr, th, skb->len))
> goto clear_hash;
> - if (tcp_md5_hash_skb_data(hp, skb, th->doff << 2))
> + if (tcp_sigpool_hash_skb_data(&hp, skb, th->doff << 2))
> goto clear_hash;
> - if (tcp_md5_hash_key(hp, key))
> + if (tcp_md5_hash_key(&hp, key))
> goto clear_hash;
> - ahash_request_set_crypt(req, NULL, md5_hash, 0);
> - if (crypto_ahash_final(req))
> + ahash_request_set_crypt(hp.req, NULL, md5_hash, 0);
> + if (crypto_ahash_final(hp.req))
> goto clear_hash;
>
> - tcp_put_md5sig_pool();
> + tcp_sigpool_end(&hp);
> return 0;
>
> clear_hash:
> - tcp_put_md5sig_pool();
> -clear_hash_noput:
> + tcp_sigpool_end(&hp);
> +clear_hash_nostart:
> memset(md5_hash, 0, 16);
> return 1;
> }
> @@ -2294,6 +2295,18 @@ static int tcp_v4_init_sock(struct sock *sk)
> return 0;
> }
>
> +#ifdef CONFIG_TCP_MD5SIG
> +static void tcp_md5sig_info_free_rcu(struct rcu_head *head)
> +{
> + struct tcp_md5sig_info *md5sig;
> +
> + md5sig = container_of(head, struct tcp_md5sig_info, rcu);
> + kfree(md5sig);
> + static_branch_slow_dec_deferred(&tcp_md5_needed);
> + tcp_md5_release_sigpool();
> +}
> +#endif
> +
> void tcp_v4_destroy_sock(struct sock *sk)
> {
> struct tcp_sock *tp = tcp_sk(sk);
> @@ -2318,10 +2331,12 @@ void tcp_v4_destroy_sock(struct sock *sk)
> #ifdef CONFIG_TCP_MD5SIG
> /* Clean up the MD5 key list, if any */
> if (tp->md5sig_info) {
> + struct tcp_md5sig_info *md5sig;
> +
> + md5sig = rcu_dereference_protected(tp->md5sig_info, 1);
> tcp_clear_md5_list(sk);
> - kfree_rcu(rcu_dereference_protected(tp->md5sig_info, 1), rcu);
> - tp->md5sig_info = NULL;
> - static_branch_slow_dec_deferred(&tcp_md5_needed);
> + call_rcu(&md5sig->rcu, tcp_md5sig_info_free_rcu);
> + rcu_assign_pointer(tp->md5sig_info, NULL);
> }
> #endif
>
> diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
> index c8f2aa003387..5616b6a34bee 100644
> --- a/net/ipv4/tcp_minisocks.c
> +++ b/net/ipv4/tcp_minisocks.c
> @@ -261,10 +261,9 @@ static void tcp_time_wait_init(struct sock *sk, struct tcp_timewait_sock *tcptw)
> tcptw->tw_md5_key = kmemdup(key, sizeof(*key), GFP_ATOMIC);
> if (!tcptw->tw_md5_key)
> return;
> - if (!tcp_alloc_md5sig_pool())
> - goto out_free;
> if (!static_key_fast_inc_not_disabled(&tcp_md5_needed.key.key))
> goto out_free;
> + tcp_md5_add_sigpool();
> }
> return;
> out_free:
> @@ -349,16 +348,26 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
> }
> EXPORT_SYMBOL(tcp_time_wait);
>
> +#ifdef CONFIG_TCP_MD5SIG
> +static void tcp_md5_twsk_free_rcu(struct rcu_head *head)
> +{
> + struct tcp_md5sig_key *key;
> +
> + key = container_of(head, struct tcp_md5sig_key, rcu);
> + kfree(key);
> + static_branch_slow_dec_deferred(&tcp_md5_needed);
> + tcp_md5_release_sigpool();
> +}
> +#endif
> +
> void tcp_twsk_destructor(struct sock *sk)
> {
> #ifdef CONFIG_TCP_MD5SIG
> if (static_branch_unlikely(&tcp_md5_needed.key)) {
> struct tcp_timewait_sock *twsk = tcp_twsk(sk);
>
> - if (twsk->tw_md5_key) {
> - kfree_rcu(twsk->tw_md5_key, rcu);
> - static_branch_slow_dec_deferred(&tcp_md5_needed);
> - }
> + if (twsk->tw_md5_key)
> + call_rcu(&twsk->tw_md5_key->rcu, tcp_md5_twsk_free_rcu);
> }
> #endif
> }
> diff --git a/net/ipv4/tcp_sigpool.c b/net/ipv4/tcp_sigpool.c
> new file mode 100644
> index 000000000000..65a8eaae2fec
> --- /dev/null
> +++ b/net/ipv4/tcp_sigpool.c
> @@ -0,0 +1,358 @@
> +// 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;
> +static DEFINE_PER_CPU(void __rcu *, sigpool_scratch);
> +
> +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());
This is wrong. num_possible_cpus() could be 2, with two cpus numbered 0 and 8.
Look for nr_cpu_ids instead.
> + 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, cpu),
> + scratch, lockdep_is_held(&cpool_mutex));
> + if (!cpu_online(cpu) || !old_scratch) {
> + kfree(old_scratch);
> + continue;
> + }
> + stf->scratches[stf->cnt++] = old_scratch;
> + }
I wonder why you are not simply using something around __alloc_percpu()
> + 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, cpu),
> + NULL, lockdep_is_held(&cpool_mutex)));
I wonder why bothering about freeing some space ? One scratch buffer
per cpu is really small.
> + __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;
> +
> + if (kref_read(&cpool[i].kref) > 0)
> + kref_get(&cpool[i].kref);
> + else
> + kref_init(&cpool[i].kref);
This looks wrong. kref_init() should be called once, after allocation,
not based on kref_read().
> + 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)
Really this looks over complicated to me.
All this kref maintenance and cpool_mutex costs :/
> +{
> + 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(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().
> + */
> + c->scratch = rcu_dereference_bh(*this_cpu_ptr(&sigpool_scratch));
> + 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);
> +
> + 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");
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 1b4529e833a1..47d798cede56 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -670,7 +670,7 @@ static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
> cmd.tcpm_key, cmd.tcpm_keylen);
> }
>
> -static int tcp_v6_md5_hash_headers(struct tcp_md5sig_pool *hp,
> +static int tcp_v6_md5_hash_headers(struct tcp_sigpool *hp,
> const struct in6_addr *daddr,
> const struct in6_addr *saddr,
> const struct tcphdr *th, int nbytes)
> @@ -691,39 +691,36 @@ static int tcp_v6_md5_hash_headers(struct tcp_md5sig_pool *hp,
> _th->check = 0;
>
> sg_init_one(&sg, bp, sizeof(*bp) + sizeof(*th));
> - ahash_request_set_crypt(hp->md5_req, &sg, NULL,
> + ahash_request_set_crypt(hp->req, &sg, NULL,
> sizeof(*bp) + sizeof(*th));
> - return crypto_ahash_update(hp->md5_req);
> + return crypto_ahash_update(hp->req);
> }
>
> static int tcp_v6_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
> const struct in6_addr *daddr, struct in6_addr *saddr,
> const struct tcphdr *th)
> {
> - struct tcp_md5sig_pool *hp;
> - struct ahash_request *req;
> + struct tcp_sigpool hp;
>
> - hp = tcp_get_md5sig_pool();
> - if (!hp)
> - goto clear_hash_noput;
> - req = hp->md5_req;
> + if (tcp_sigpool_start(tcp_md5_sigpool_id, &hp))
> + goto clear_hash_nostart;
>
> - if (crypto_ahash_init(req))
> + if (crypto_ahash_init(hp.req))
> goto clear_hash;
> - if (tcp_v6_md5_hash_headers(hp, daddr, saddr, th, th->doff << 2))
> + if (tcp_v6_md5_hash_headers(&hp, daddr, saddr, th, th->doff << 2))
> goto clear_hash;
> - if (tcp_md5_hash_key(hp, key))
> + if (tcp_md5_hash_key(&hp, key))
> goto clear_hash;
> - ahash_request_set_crypt(req, NULL, md5_hash, 0);
> - if (crypto_ahash_final(req))
> + ahash_request_set_crypt(hp.req, NULL, md5_hash, 0);
> + if (crypto_ahash_final(hp.req))
> goto clear_hash;
>
> - tcp_put_md5sig_pool();
> + tcp_sigpool_end(&hp);
> return 0;
>
> clear_hash:
> - tcp_put_md5sig_pool();
> -clear_hash_noput:
> + tcp_sigpool_end(&hp);
> +clear_hash_nostart:
> memset(md5_hash, 0, 16);
> return 1;
> }
> @@ -733,10 +730,9 @@ static int tcp_v6_md5_hash_skb(char *md5_hash,
> const struct sock *sk,
> const struct sk_buff *skb)
> {
> - const struct in6_addr *saddr, *daddr;
> - struct tcp_md5sig_pool *hp;
> - struct ahash_request *req;
> const struct tcphdr *th = tcp_hdr(skb);
> + const struct in6_addr *saddr, *daddr;
> + struct tcp_sigpool hp;
>
> if (sk) { /* valid for establish/request sockets */
> saddr = &sk->sk_v6_rcv_saddr;
> @@ -747,30 +743,28 @@ static int tcp_v6_md5_hash_skb(char *md5_hash,
> daddr = &ip6h->daddr;
> }
>
> - hp = tcp_get_md5sig_pool();
> - if (!hp)
> - goto clear_hash_noput;
> - req = hp->md5_req;
> + if (tcp_sigpool_start(tcp_md5_sigpool_id, &hp))
> + goto clear_hash_nostart;
>
> - if (crypto_ahash_init(req))
> + if (crypto_ahash_init(hp.req))
> goto clear_hash;
>
> - if (tcp_v6_md5_hash_headers(hp, daddr, saddr, th, skb->len))
> + if (tcp_v6_md5_hash_headers(&hp, daddr, saddr, th, skb->len))
> goto clear_hash;
> - if (tcp_md5_hash_skb_data(hp, skb, th->doff << 2))
> + if (tcp_sigpool_hash_skb_data(&hp, skb, th->doff << 2))
> goto clear_hash;
> - if (tcp_md5_hash_key(hp, key))
> + if (tcp_md5_hash_key(&hp, key))
> goto clear_hash;
> - ahash_request_set_crypt(req, NULL, md5_hash, 0);
> - if (crypto_ahash_final(req))
> + ahash_request_set_crypt(hp.req, NULL, md5_hash, 0);
> + if (crypto_ahash_final(hp.req))
> goto clear_hash;
>
> - tcp_put_md5sig_pool();
> + tcp_sigpool_end(&hp);
> return 0;
>
> clear_hash:
> - tcp_put_md5sig_pool();
> -clear_hash_noput:
> + tcp_sigpool_end(&hp);
> +clear_hash_nostart:
> memset(md5_hash, 0, 16);
> return 1;
> }
> --
> 2.41.0
>