[Devel] [PATCH RHEL7 COMMIT] ms/crypto: af_alg - Disallow bind/setkey/... after accept(2)

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.36.1.vz7.19.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.36.1.vz7.19.3
------>
commit 5eaf3ae7d1201d8fb193341b51e135039d213476
Author: Herbert Xu <herbert at gondor.apana.org.au>
Date:   Mon Oct 24 16:34:02 2016 +0400

    ms/crypto: af_alg - Disallow bind/setkey/... after accept(2)
    
    Each af_alg parent socket obtained by socket(2) corresponds to a
    tfm object once bind(2) has succeeded.  An accept(2) call on that
    parent socket creates a context which then uses the tfm object.
    
    Therefore as long as any child sockets created by accept(2) exist
    the parent socket must not be modified or freed.
    
    This patch guarantees this by using locks and a reference count
    on the parent socket.  Any attempt to modify the parent socket will
    fail with EBUSY.
    
    Cc: stable at vger.kernel.org
    Reported-by: Dmitry Vyukov <dvyukov at google.com>
    Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>
    (cherry picked from commit c840ac6af3f8713a71b4d2363419145760bd6044)
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 crypto/af_alg.c         | 35 ++++++++++++++++++++++++++++++++---
 include/crypto/if_alg.h |  8 +++-----
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index bf948e1..4311214 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -125,6 +125,23 @@ int af_alg_release(struct socket *sock)
 }
 EXPORT_SYMBOL_GPL(af_alg_release);
 
+void af_alg_release_parent(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	bool last;
+
+	sk = ask->parent;
+	ask = alg_sk(sk);
+
+	lock_sock(sk);
+	last = !--ask->refcnt;
+	release_sock(sk);
+
+	if (last)
+		sock_put(sk);
+}
+EXPORT_SYMBOL_GPL(af_alg_release_parent);
+
 static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 {
 	struct sock *sk = sock->sk;
@@ -132,6 +149,7 @@ static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	struct sockaddr_alg *sa = (void *)uaddr;
 	const struct af_alg_type *type;
 	void *private;
+	int err;
 
 	if (sock->state == SS_CONNECTED)
 		return -EINVAL;
@@ -157,16 +175,22 @@ static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 		return PTR_ERR(private);
 	}
 
+	err = -EBUSY;
 	lock_sock(sk);
+	if (ask->refcnt)
+		goto unlock;
 
 	swap(ask->type, type);
 	swap(ask->private, private);
 
+	err = 0;
+
+unlock:
 	release_sock(sk);
 
 	alg_do_release(type, private);
 
-	return 0;
+	return err;
 }
 
 static int alg_setkey(struct sock *sk, char __user *ukey,
@@ -199,11 +223,15 @@ static int alg_setsockopt(struct socket *sock, int level, int optname,
 	struct sock *sk = sock->sk;
 	struct alg_sock *ask = alg_sk(sk);
 	const struct af_alg_type *type;
-	int err = -ENOPROTOOPT;
+	int err = -EBUSY;
 
 	lock_sock(sk);
+	if (ask->refcnt)
+		goto unlock;
+
 	type = ask->type;
 
+	err = -ENOPROTOOPT;
 	if (level != SOL_ALG || !type)
 		goto unlock;
 
@@ -254,7 +282,8 @@ int af_alg_accept(struct sock *sk, struct socket *newsock)
 
 	sk2->sk_family = PF_ALG;
 
-	sock_hold(sk);
+	if (!ask->refcnt++)
+		sock_hold(sk);
 	alg_sk(sk2)->parent = sk;
 	alg_sk(sk2)->type = type;
 
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index d61c111..2f38daa 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -30,6 +30,8 @@ struct alg_sock {
 
 	struct sock *parent;
 
+	unsigned int refcnt;
+
 	const struct af_alg_type *type;
 	void *private;
 };
@@ -64,6 +66,7 @@ int af_alg_register_type(const struct af_alg_type *type);
 int af_alg_unregister_type(const struct af_alg_type *type);
 
 int af_alg_release(struct socket *sock);
+void af_alg_release_parent(struct sock *sk);
 int af_alg_accept(struct sock *sk, struct socket *newsock);
 
 int af_alg_make_sg(struct af_alg_sgl *sgl, void __user *addr, int len,
@@ -80,11 +83,6 @@ static inline struct alg_sock *alg_sk(struct sock *sk)
 	return (struct alg_sock *)sk;
 }
 
-static inline void af_alg_release_parent(struct sock *sk)
-{
-	sock_put(alg_sk(sk)->parent);
-}
-
 static inline void af_alg_init_completion(struct af_alg_completion *completion)
 {
 	init_completion(&completion->completion);