linux-kernel - [PATCH 4.14 38/74] crypto: af_alg - fix race accessing cipher request

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Date:   Wed, 27 Dec 2017 17:46:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, syzbot <syzkaller@...glegroups.com>,
        Stephan Mueller <smueller@...onox.de>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.14 38/74] crypto: af_alg - fix race accessing cipher request

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

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

From: Stephan Mueller <smueller@...onox.de>

commit d53c5135792319e095bb126bc43b2ee98586f7fe upstream.

When invoking an asynchronous cipher operation, the invocation of the
callback may be performed before the subsequent operations in the
initial code path are invoked. The callback deletes the cipher request
data structure which implies that after the invocation of the
asynchronous cipher operation, this data structure must not be accessed
any more.

The setting of the return code size with the request data structure must
therefore be moved before the invocation of the asynchronous cipher
operation.

Fixes: e870456d8e7c ("crypto: algif_skcipher - overhaul memory management")
Fixes: d887c52d6ae4 ("crypto: algif_aead - overhaul memory management")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Stephan Mueller <smueller@...onox.de>
Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 crypto/algif_aead.c     |   10 +++++-----
 crypto/algif_skcipher.c |   10 +++++-----
 2 files changed, 10 insertions(+), 10 deletions(-)

--- a/crypto/algif_aead.c
+++ b/crypto/algif_aead.c
@@ -291,6 +291,10 @@ static int _aead_recvmsg(struct socket *
 		/* AIO operation */
 		sock_hold(sk);
 		areq->iocb = msg->msg_iocb;
+
+		/* Remember output size that will be generated. */
+		areq->outlen = outlen;
+
 		aead_request_set_callback(&areq->cra_u.aead_req,
 					  CRYPTO_TFM_REQ_MAY_BACKLOG,
 					  af_alg_async_cb, areq);
@@ -298,12 +302,8 @@ static int _aead_recvmsg(struct socket *
 				 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;
-
+		if (err == -EINPROGRESS || err == -EBUSY)
 			return -EIOCBQUEUED;
-		}
 
 		sock_put(sk);
 	} else {
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -125,6 +125,10 @@ static int _skcipher_recvmsg(struct sock
 		/* AIO operation */
 		sock_hold(sk);
 		areq->iocb = msg->msg_iocb;
+
+		/* Remember output size that will be generated. */
+		areq->outlen = len;
+
 		skcipher_request_set_callback(&areq->cra_u.skcipher_req,
 					      CRYPTO_TFM_REQ_MAY_SLEEP,
 					      af_alg_async_cb, areq);
@@ -133,12 +137,8 @@ static int _skcipher_recvmsg(struct sock
 			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;
-
+		if (err == -EINPROGRESS || err == -EBUSY)
 			return -EIOCBQUEUED;
-		}
 
 		sock_put(sk);
 	} else {