[PATCH] af_key: Fix send_acquire race with pfkey_register

[Herbert Xu]

With name space support, it is possible for a pfkey_register to
occur in the middle of a send_acquire, thus changing the number
of supported algorithms.

This can be fixed by taking a mutex to make it single-threaded
again.

Reported-by: syzbot+1e9af9185d8850e2c2fa@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 283bc9f35bbb ("xfrm: Namespacify xfrm state/policy locks")
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

diff --git a/net/key/af_key.c b/net/key/af_key.c
index c85df5b958d2..4ceef96fef57 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -3160,6 +3160,7 @@ static int pfkey_send_acquire(struct xfrm_state *x, struct xfrm_tmpl *t, struct
 		(sockaddr_size * 2) +
 		sizeof(struct sadb_x_policy);
 
+	mutex_lock(&pfkey_mutex);
 	if (x->id.proto == IPPROTO_AH)
 		size += count_ah_combs(t);
 	else if (x->id.proto == IPPROTO_ESP)
@@ -3171,8 +3172,10 @@ static int pfkey_send_acquire(struct xfrm_state *x, struct xfrm_tmpl *t, struct
 	}
 
 	skb =  alloc_skb(size + 16, GFP_ATOMIC);
-	if (skb == NULL)
+	if (skb == NULL) {
+		mutex_unlock(&pfkey_mutex);
 		return -ENOMEM;
+	}
 
 	hdr = skb_put(skb, sizeof(struct sadb_msg));
 	hdr->sadb_msg_version = PF_KEY_V2;
@@ -3228,6 +3231,7 @@ static int pfkey_send_acquire(struct xfrm_state *x, struct xfrm_tmpl *t, struct
 		dump_ah_combs(skb, t);
 	else if (x->id.proto == IPPROTO_ESP)
 		dump_esp_combs(skb, t);
+	mutex_unlock(&pfkey_mutex);
 
 	/* security context */
 	if (xfrm_ctx) {
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt