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Miller" , Eric Dumazet , Antonio Quartulli Subject: [PATCH net 4/4] ovpn: defer key slot crypto freeing to workqueue Date: Fri, 7 Aug 2026 02:22:44 +0200 Message-ID: <20260807002250.1817498-5-antonio@openvpn.net> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260807002250.1817498-1-antonio@openvpn.net> References: <20260807002250.1817498-1-antonio@openvpn.net> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ralf Lici Key slots are released through a kref and the existing release path frees the AEAD transforms from an RCU callback. That is not safe for all crypto implementations: crypto_free_aead can sleep, for example when an async or hardware implementation has teardown work to complete. Use queue_rcu_work for key-slot release. This keeps the RCU grace period needed by lockless key-slot readers, but runs the actual crypto teardown from workqueue context where sleeping is allowed. Once the rcu_work callback runs, pre-existing RCU readers are gone, and the final kref put already proves that no transform user remains, so the worker can release the AEAD transforms and free the slot directly. The previous patch drains ovpn_wq during module exit, so queued key-slot teardown work cannot outlive module text. Fixes: 8534731dbf2d ("ovpn: implement packet processing") Signed-off-by: Ralf Lici Signed-off-by: Antonio Quartulli --- drivers/net/ovpn/crypto.c | 10 +--------- drivers/net/ovpn/crypto.h | 4 +++- drivers/net/ovpn/crypto_aead.c | 19 ++++++++++++++----- drivers/net/ovpn/crypto_aead.h | 1 - 4 files changed, 18 insertions(+), 16 deletions(-) diff --git a/drivers/net/ovpn/crypto.c b/drivers/net/ovpn/crypto.c index 2e95f29514fc..7e545428900a 100644 --- a/drivers/net/ovpn/crypto.c +++ b/drivers/net/ovpn/crypto.c @@ -18,20 +18,12 @@ #include "crypto_aead.h" #include "crypto.h" -static void ovpn_ks_destroy_rcu(struct rcu_head *head) -{ - struct ovpn_crypto_key_slot *ks; - - ks = container_of(head, struct ovpn_crypto_key_slot, rcu); - ovpn_aead_crypto_key_slot_destroy(ks); -} - void ovpn_crypto_key_slot_release(struct kref *kref) { struct ovpn_crypto_key_slot *ks; ks = container_of(kref, struct ovpn_crypto_key_slot, refcount); - call_rcu(&ks->rcu, ovpn_ks_destroy_rcu); + queue_rcu_work(ovpn_wq, &ks->free_work); } /* can only be invoked when all peer references have been dropped (i.e. RCU diff --git a/drivers/net/ovpn/crypto.h b/drivers/net/ovpn/crypto.h index 0e284fec3a75..e3feb16d5498 100644 --- a/drivers/net/ovpn/crypto.h +++ b/drivers/net/ovpn/crypto.h @@ -10,6 +10,8 @@ #ifndef _NET_OVPN_OVPNCRYPTO_H_ #define _NET_OVPN_OVPNCRYPTO_H_ +#include + #include "pktid.h" #include "proto.h" @@ -45,8 +47,8 @@ struct ovpn_crypto_key_slot { struct ovpn_pktid_recv pid_recv ____cacheline_aligned_in_smp; struct ovpn_pktid_xmit pid_xmit ____cacheline_aligned_in_smp; + struct rcu_work free_work; struct kref refcount; - struct rcu_head rcu; }; struct ovpn_crypto_state { diff --git a/drivers/net/ovpn/crypto_aead.c b/drivers/net/ovpn/crypto_aead.c index 8f07c418622b..74eaf6fac2f5 100644 --- a/drivers/net/ovpn/crypto_aead.c +++ b/drivers/net/ovpn/crypto_aead.c @@ -9,6 +9,7 @@ #include #include +#include #include #include #include @@ -380,13 +381,19 @@ static struct crypto_aead *ovpn_aead_init(const char *title, return ERR_PTR(ret); } -void ovpn_aead_crypto_key_slot_destroy(struct ovpn_crypto_key_slot *ks) +static void ovpn_aead_crypto_key_slot_free(struct ovpn_crypto_key_slot *ks) { - if (!ks) - return; - crypto_free_aead(ks->encrypt); crypto_free_aead(ks->decrypt); +} + +static void ovpn_aead_crypto_key_slot_free_work(struct work_struct *work) +{ + struct ovpn_crypto_key_slot *ks; + + ks = container_of(to_rcu_work(work), struct ovpn_crypto_key_slot, + free_work); + ovpn_aead_crypto_key_slot_free(ks); kfree(ks); } @@ -420,6 +427,7 @@ ovpn_aead_crypto_key_slot_new(const struct ovpn_key_config *kc) ks->encrypt = NULL; ks->decrypt = NULL; + INIT_RCU_WORK(&ks->free_work, ovpn_aead_crypto_key_slot_free_work); kref_init(&ks->refcount); ks->key_id = kc->key_id; @@ -453,7 +461,8 @@ ovpn_aead_crypto_key_slot_new(const struct ovpn_key_config *kc) return ks; destroy_ks: - ovpn_aead_crypto_key_slot_destroy(ks); + ovpn_aead_crypto_key_slot_free(ks); + kfree(ks); return ERR_PTR(ret); } diff --git a/drivers/net/ovpn/crypto_aead.h b/drivers/net/ovpn/crypto_aead.h index 65a2ff307898..fae3b585a43b 100644 --- a/drivers/net/ovpn/crypto_aead.h +++ b/drivers/net/ovpn/crypto_aead.h @@ -22,7 +22,6 @@ int ovpn_aead_decrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks, struct ovpn_crypto_key_slot * ovpn_aead_crypto_key_slot_new(const struct ovpn_key_config *kc); -void ovpn_aead_crypto_key_slot_destroy(struct ovpn_crypto_key_slot *ks); enum ovpn_cipher_alg ovpn_aead_crypto_alg(struct ovpn_crypto_key_slot *ks); -- 2.54.0