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    Subject[PATCH 4.4 107/117] crypto: algif_skcipher - Do not dereference ctx without socket lock
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

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

    commit 6454c2b83f719057069777132b13949e4c6b6350 upstream.

    Any access to non-constant bits of the private context must be
    done under the socket lock, in particular, this includes ctx->req.

    This patch moves such accesses under the lock, and fetches the
    tfm from the parent socket which is guaranteed to be constant,
    rather than from ctx->req.

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

    ---
    crypto/algif_skcipher.c | 15 +++++++++++----
    1 file changed, 11 insertions(+), 4 deletions(-)

    --- a/crypto/algif_skcipher.c
    +++ b/crypto/algif_skcipher.c
    @@ -295,8 +295,11 @@ static int skcipher_sendmsg(struct socke
    {
    struct sock *sk = sock->sk;
    struct alg_sock *ask = alg_sk(sk);
    + struct sock *psk = ask->parent;
    + struct alg_sock *pask = alg_sk(psk);
    struct skcipher_ctx *ctx = ask->private;
    - struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(&ctx->req);
    + struct skcipher_tfm *skc = pask->private;
    + struct crypto_skcipher *tfm = skc->skcipher;
    unsigned ivsize = crypto_skcipher_ivsize(tfm);
    struct skcipher_sg_list *sgl;
    struct af_alg_control con = {};
    @@ -508,7 +511,7 @@ static int skcipher_recvmsg_async(struct
    struct skcipher_async_req *sreq;
    struct skcipher_request *req;
    struct skcipher_async_rsgl *last_rsgl = NULL;
    - unsigned int txbufs = 0, len = 0, tx_nents = skcipher_all_sg_nents(ctx);
    + unsigned int txbufs = 0, len = 0, tx_nents;
    unsigned int reqsize = crypto_skcipher_reqsize(tfm);
    unsigned int ivsize = crypto_skcipher_ivsize(tfm);
    int err = -ENOMEM;
    @@ -526,6 +529,7 @@ static int skcipher_recvmsg_async(struct
    sreq->inflight = &ctx->inflight;

    lock_sock(sk);
    + tx_nents = skcipher_all_sg_nents(ctx);
    sreq->tsg = kcalloc(tx_nents, sizeof(*sg), GFP_KERNEL);
    if (unlikely(!sreq->tsg))
    goto unlock;
    @@ -633,9 +637,12 @@ static int skcipher_recvmsg_sync(struct
    {
    struct sock *sk = sock->sk;
    struct alg_sock *ask = alg_sk(sk);
    + struct sock *psk = ask->parent;
    + struct alg_sock *pask = alg_sk(psk);
    struct skcipher_ctx *ctx = ask->private;
    - unsigned bs = crypto_skcipher_blocksize(crypto_skcipher_reqtfm(
    - &ctx->req));
    + struct skcipher_tfm *skc = pask->private;
    + struct crypto_skcipher *tfm = skc->skcipher;
    + unsigned bs = crypto_skcipher_blocksize(tfm);
    struct skcipher_sg_list *sgl;
    struct scatterlist *sg;
    int err = -EAGAIN;

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