[PATCH 4.2.y-ckt 004/218] crypto: algif_skcipher - Do not dereference ctx without socket lock

[Kamal Mostafa]

4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxx>
[ kamal: backport to 4.2-stable: use ablkcipher ]
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
 crypto/algif_skcipher.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 1939e60..42e497d 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -295,8 +295,11 @@ static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg,
 {
 	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_ablkcipher *tfm = crypto_ablkcipher_reqtfm(&ctx->req);
+	struct skcipher_tfm *skc = pask->private;
+	struct crypto_ablkcipher *tfm = skc->skcipher;
 	unsigned ivsize = crypto_ablkcipher_ivsize(tfm);
 	struct skcipher_sg_list *sgl;
 	struct af_alg_control con = {};
@@ -508,7 +511,7 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg,
 	struct skcipher_async_req *sreq;
 	struct ablkcipher_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_ablkcipher_reqsize(tfm);
 	unsigned int ivsize = crypto_ablkcipher_ivsize(tfm);
 	int err = -ENOMEM;
@@ -526,6 +529,7 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg,
 	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 socket *sock, struct msghdr *msg,
 {
 	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_ablkcipher_blocksize(crypto_ablkcipher_reqtfm(
-		&ctx->req));
+	struct skcipher_tfm *skc = pask->private;
+	struct crypto_ablkcipher *tfm = skc->skcipher;
+	unsigned bs = crypto_ablkcipher_blocksize(tfm);
 	struct skcipher_sg_list *sgl;
 	struct scatterlist *sg;
 	int err = -EAGAIN;
-- 
2.7.4