crypto: af_alg - remove locking in async callback

The code paths protected by the socket-lock do not use or modify the
socket in a non-atomic fashion. The actions pertaining the socket do not
even need to be handled as an atomic operation. Thus, the socket-lock
can be safely ignored.

This fixes a bug regarding scheduling in atomic as the callback function
may be invoked in interrupt context.

In addition, the sock_hold is moved before the AIO encrypt/decrypt
operation to ensure that the socket is always present. This avoids a
tiny race window where the socket is unprotected and yet used by the AIO
operation.

Finally, the release of resources for a crypto operation is moved into a
common function of af_alg_free_resources.

Cc: <stable@vger.kernel.org>
Fixes: e870456d8e7c8 ("crypto: algif_skcipher - overhaul memory management")
Fixes: d887c52d6ae43 ("crypto: algif_aead - overhaul memory management")
Reported-by: Romain Izard <romain.izard.pro@gmail.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Tested-by: Romain Izard <romain.izard.pro@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

4 files changed, 39 insertions, 29 deletions

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 85cea9de324a..358749c38894 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1021,6 +1021,18 @@ unlock:
 EXPORT_SYMBOL_GPL(af_alg_sendpage);
 
 /**
+ * af_alg_free_resources - release resources required for crypto request
+ */
+void af_alg_free_resources(struct af_alg_async_req *areq)
+{
+        struct sock *sk = areq->sk;
+
+        af_alg_free_areq_sgls(areq);
+        sock_kfree_s(sk, areq, areq->areqlen);
+}
+EXPORT_SYMBOL_GPL(af_alg_free_resources);
+
+/**
  * af_alg_async_cb - AIO callback handler
  *
  * This handler cleans up the struct af_alg_async_req upon completion of the
@@ -1036,18 +1048,13 @@ void af_alg_async_cb(struct crypto_async_request *_req, int err)
         struct kiocb *iocb = areq->iocb;
         unsigned int resultlen;
 
-        lock_sock(sk);
-
         /* Buffer size written by crypto operation. */
         resultlen = areq->outlen;
 
-        af_alg_free_areq_sgls(areq);
-        sock_kfree_s(sk, areq, areq->areqlen);
-        __sock_put(sk);
+        af_alg_free_resources(areq);
+        sock_put(sk);
 
         iocb->ki_complete(iocb, err ? err : resultlen, 0);
-
-        release_sock(sk);
 }
 EXPORT_SYMBOL_GPL(af_alg_async_cb);
 
diff --git a/crypto/algif_aead.c b/crypto/algif_aead.c
index e2068b78993c..805f485ddf1b 100644
--- a/crypto/algif_aead.c
+++ b/crypto/algif_aead.c
@@ -283,12 +283,23 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
 
         if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
                 /* AIO operation */
+                sock_hold(sk);
                 areq->iocb = msg->msg_iocb;
                 aead_request_set_callback(&areq->cra_u.aead_req,
                                           CRYPTO_TFM_REQ_MAY_BACKLOG,
                                           af_alg_async_cb, areq);
                 err = ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_req) :
                                  crypto_aead_decrypt(&areq->cra_u.aead_req);
+
+                /* AIO operation in progress */
+                if (err == -EINPROGRESS || err == -EBUSY) {
+                        /* Remember output size that will be generated. */
+                        areq->outlen = outlen;
+
+                        return -EIOCBQUEUED;
+                }
+
+                sock_put(sk);
         } else {
                 /* Synchronous operation */
                 aead_request_set_callback(&areq->cra_u.aead_req,
@@ -300,19 +311,9 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
                                 &ctx->wait);
         }
 
-        /* AIO operation in progress */
-        if (err == -EINPROGRESS) {
-                sock_hold(sk);
-
-                /* Remember output size that will be generated. */
-                areq->outlen = outlen;
-
-                return -EIOCBQUEUED;
-        }
 
 free:
-        af_alg_free_areq_sgls(areq);
-        sock_kfree_s(sk, areq, areq->areqlen);
+        af_alg_free_resources(areq);
 
         return err ? err : outlen;
 }
diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 9954b078f0b9..30cff827dd8f 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -117,6 +117,7 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
 
         if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
                 /* AIO operation */
+                sock_hold(sk);
                 areq->iocb = msg->msg_iocb;
                 skcipher_request_set_callback(&areq->cra_u.skcipher_req,
                                               CRYPTO_TFM_REQ_MAY_SLEEP,
@@ -124,6 +125,16 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
                 err = ctx->enc ?
                         crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
                         crypto_skcipher_decrypt(&areq->cra_u.skcipher_req);
+
+                /* AIO operation in progress */
+                if (err == -EINPROGRESS || err == -EBUSY) {
+                        /* Remember output size that will be generated. */
+                        areq->outlen = len;
+
+                        return -EIOCBQUEUED;
+                }
+
+                sock_put(sk);
         } else {
                 /* Synchronous operation */
                 skcipher_request_set_callback(&areq->cra_u.skcipher_req,
@@ -136,19 +147,9 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
                                                  &ctx->wait);
         }
 
-        /* AIO operation in progress */
-        if (err == -EINPROGRESS) {
-                sock_hold(sk);
-
-                /* Remember output size that will be generated. */
-                areq->outlen = len;
-
-                return -EIOCBQUEUED;
-        }
 
 free:
-        af_alg_free_areq_sgls(areq);
-        sock_kfree_s(sk, areq, areq->areqlen);
+        af_alg_free_resources(areq);
 
         return err ? err : len;
 }
diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index 6abf0a3604dc..38d9c5861ed8 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -242,6 +242,7 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
                    unsigned int ivsize);
 ssize_t af_alg_sendpage(struct socket *sock, struct page *page,
                         int offset, size_t size, int flags);
+void af_alg_free_resources(struct af_alg_async_req *areq);
 void af_alg_async_cb(struct crypto_async_request *_req, int err);
 unsigned int af_alg_poll(struct file *file, struct socket *sock,
                          poll_table *wait);