crypto: algif_skcipher - Do not dereference ctx without socket lock

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.

Cc: stable@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 11 insertions, 4 deletions

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index ec07a864b9c5..ef84353e0f24 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_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 socket *sock, struct msghdr *msg,
         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 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_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;