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    Subject[PATCH 4.3 174/200] crypto: algif_skcipher - Fix race condition in skcipher_check_key
    Date
    4.3-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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;
    }

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