[PATCH 4.4 096/117] crypto: algif_skcipher - Fix race condition in skcipher_check_key

Greg Kroah-Hartman
2016-02-15T00:24:39Z

From: Herbert Xu <herbert@gondor.apana.org.au>

commit 1822793a523e5d5730b19cc21160ff1717421bc8 upstream.

We need to lock the child socket in skcipher_check_key as otherwise
two simultaneous calls can cause the parent socket to be freed.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
crypto/algif_skcipher.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -755,22 +755,23 @@ static struct proto_ops algif_skcipher_o

static int skcipher_check_key(struct socket *sock)
{
- int err;
+ int err = 0;
struct sock *psk;
struct alg_sock *pask;
struct skcipher_tfm *tfm;
struct sock *sk = sock->sk;
struct alg_sock *ask = alg_sk(sk);

+ lock_sock(sk);
if (ask->refcnt)
- return 0;
+ goto unlock_child;

psk = ask->parent;
pask = alg_sk(ask->parent);
tfm = pask->private;

err = -ENOKEY;
- lock_sock(psk);
+ lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
if (!tfm->has_key)
goto unlock;

@@ -784,6 +785,8 @@ static int skcipher_check_key(struct soc

unlock:
release_sock(psk);
+unlock_child:
+ release_sock(sk);

return err;
}