af_key: Add lock to key dump

A dump may come in the middle of another dump, modifying its dump
structure members. This race condition will result in NULL pointer
dereference in kernel. So add a lock to prevent that race.

Fixes: 83321d6b9872 ("[AF_KEY]: Dump SA/SP entries non-atomically")
Signed-off-by: Yuejie Shi <syjcnss@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/key/af_key.c b/net/key/af_key.c
index c6252ed42c1de65dee149d7d869b62b96616e22a..1b0ea80133f1bba992681af2ab4c337db3cdc63d 100644 (file)
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -63,6 +63,7 @@ struct pfkey_sock {
                } u;
                struct sk_buff  *skb;
        } dump;
+       struct mutex dump_lock;
 };
 
 static inline struct pfkey_sock *pfkey_sk(struct sock *sk)
@@ -139,6 +140,7 @@ static int pfkey_create(struct net *net, struct socket *sock, int protocol,
 {
        struct netns_pfkey *net_pfkey = net_generic(net, pfkey_net_id);
        struct sock *sk;
+       struct pfkey_sock *pfk;
        int err;
 
        if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
@@ -153,6 +155,9 @@ static int pfkey_create(struct net *net, struct socket *sock, int protocol,
        if (sk == NULL)
                goto out;
 
+       pfk = pfkey_sk(sk);
+       mutex_init(&pfk->dump_lock);
+
        sock->ops = &pfkey_ops;
        sock_init_data(sock, sk);
 
@@ -281,13 +286,23 @@ static int pfkey_do_dump(struct pfkey_sock *pfk)
        struct sadb_msg *hdr;
        int rc;
 
+       mutex_lock(&pfk->dump_lock);
+       if (!pfk->dump.dump) {
+               rc = 0;
+               goto out;
+       }
+
        rc = pfk->dump.dump(pfk);
-       if (rc == -ENOBUFS)
-               return 0;
+       if (rc == -ENOBUFS) {
+               rc = 0;
+               goto out;
+       }
 
        if (pfk->dump.skb) {
-               if (!pfkey_can_dump(&pfk->sk))
-                       return 0;
+               if (!pfkey_can_dump(&pfk->sk)) {
+                       rc = 0;
+                       goto out;
+               }
 
                hdr = (struct sadb_msg *) pfk->dump.skb->data;
                hdr->sadb_msg_seq = 0;
@@ -298,6 +313,9 @@ static int pfkey_do_dump(struct pfkey_sock *pfk)
        }
 
        pfkey_terminate_dump(pfk);
+
+out:
+       mutex_unlock(&pfk->dump_lock);
        return rc;
 }
 
@@ -1793,19 +1811,26 @@ static int pfkey_dump(struct sock *sk, struct sk_buff *skb, const struct sadb_ms
        struct xfrm_address_filter *filter = NULL;
        struct pfkey_sock *pfk = pfkey_sk(sk);
 
-       if (pfk->dump.dump != NULL)
+       mutex_lock(&pfk->dump_lock);
+       if (pfk->dump.dump != NULL) {
+               mutex_unlock(&pfk->dump_lock);
                return -EBUSY;
+       }
 
        proto = pfkey_satype2proto(hdr->sadb_msg_satype);
-       if (proto == 0)
+       if (proto == 0) {
+               mutex_unlock(&pfk->dump_lock);
                return -EINVAL;
+       }
 
        if (ext_hdrs[SADB_X_EXT_FILTER - 1]) {
                struct sadb_x_filter *xfilter = ext_hdrs[SADB_X_EXT_FILTER - 1];
 
                filter = kmalloc(sizeof(*filter), GFP_KERNEL);
-               if (filter == NULL)
+               if (filter == NULL) {
+                       mutex_unlock(&pfk->dump_lock);
                        return -ENOMEM;
+               }
 
                memcpy(&filter->saddr, &xfilter->sadb_x_filter_saddr,
                       sizeof(xfrm_address_t));
@@ -1821,6 +1846,7 @@ static int pfkey_dump(struct sock *sk, struct sk_buff *skb, const struct sadb_ms
        pfk->dump.dump = pfkey_dump_sa;
        pfk->dump.done = pfkey_dump_sa_done;
        xfrm_state_walk_init(&pfk->dump.u.state, proto, filter);
+       mutex_unlock(&pfk->dump_lock);
 
        return pfkey_do_dump(pfk);
 }
@@ -2679,14 +2705,18 @@ static int pfkey_spddump(struct sock *sk, struct sk_buff *skb, const struct sadb
 {
        struct pfkey_sock *pfk = pfkey_sk(sk);
 
-       if (pfk->dump.dump != NULL)
+       mutex_lock(&pfk->dump_lock);
+       if (pfk->dump.dump != NULL) {
+               mutex_unlock(&pfk->dump_lock);
                return -EBUSY;
+       }
 
        pfk->dump.msg_version = hdr->sadb_msg_version;
        pfk->dump.msg_portid = hdr->sadb_msg_pid;
        pfk->dump.dump = pfkey_dump_sp;
        pfk->dump.done = pfkey_dump_sp_done;
        xfrm_policy_walk_init(&pfk->dump.u.policy, XFRM_POLICY_TYPE_MAIN);
+       mutex_unlock(&pfk->dump_lock);
 
        return pfkey_do_dump(pfk);
 }