ovpn: defer key slot crypto freeing to workqueue

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 <ralf@mandelbit.com>
Signed-off-by: Antonio Quartulli <antonio@openvpn.net>

diff --git a/drivers/net/ovpn/crypto.c b/drivers/net/ovpn/crypto.c
index 2e95f29514fc4a527b1bb157092ca98e2bd025f0..7e545428900a995f8f88ba02d648d220652210c4 100644 (file)
--- 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 0e284fec3a75a0a5933978ea9d136f87a2e5c57a..e3feb16d549853165214dca0c4a6ca5436ee8721 100644 (file)
--- 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 <linux/workqueue.h>
+
 #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 8f07c418622b255db5031fe5098e533698d25f39..74eaf6fac2f525661082b615917ab5f883ab33a9 100644 (file)
--- a/drivers/net/ovpn/crypto_aead.c
+++ b/drivers/net/ovpn/crypto_aead.c
@@ -9,6 +9,7 @@
 
 #include <crypto/aead.h>
 #include <linux/skbuff.h>
+#include <linux/workqueue.h>
 #include <net/ip.h>
 #include <net/ipv6.h>
 #include <net/udp.h>
@@ -380,13 +381,19 @@ error:
        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 65a2ff30789862bf52bbda389a995f8edff48e7e..fae3b585a43b33eeea5f39483cfb3187572742c8 100644 (file)
--- 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);