From: Romain Izard Subject: Re: [PATCH v3] crypto: AF_ALG - remove locking in async callback Date: Fri, 10 Nov 2017 17:50:48 +0100 Message-ID: References: <2510520.gYBNS8MAsP@positron.chronox.de> <20171110111058.GA25914@gondor.apana.org.au> <1966139.WIlnTlQG5u@positron.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Cc: Herbert Xu , linux-crypto@vger.kernel.org, Cyrille Pitchen , Tudor Ambarus , Nicolas Ferre , linux-arm-kernel To: =?UTF-8?Q?Stephan_M=C3=BCller?= Return-path: Received: from mail-qk0-f193.google.com ([209.85.220.193]:47432 "EHLO mail-qk0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbdKJQvJ (ORCPT ); Fri, 10 Nov 2017 11:51:09 -0500 Received: by mail-qk0-f193.google.com with SMTP id 136so1785524qkd.4 for ; Fri, 10 Nov 2017 08:51:09 -0800 (PST) In-Reply-To: <1966139.WIlnTlQG5u@positron.chronox.de> Sender: linux-crypto-owner@vger.kernel.org List-ID: 2017-11-10 13:20 GMT+01:00 Stephan M=C3=BCller : > 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. > > Fixes: e870456d8e7c8 ("crypto: algif_skcipher - overhaul memory managemen= t") > Fixes: d887c52d6ae43 ("crypto: algif_aead - overhaul memory management") > Reported-by: Romain Izard > Signed-off-by: Stephan Mueller Tested-by: Romain Izard On 4.14-rc8, with some fuzzing when applying the patch. The deterministic crash is not reproduced. > --- > crypto/af_alg.c | 21 ++++++++++++++------- > crypto/algif_aead.c | 23 ++++++++++++----------- > crypto/algif_skcipher.c | 23 ++++++++++++----------- > include/crypto/if_alg.h | 1 + > 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 @@ ssize_t af_alg_sendpage(struct socket *sock, struc= t page *page, > 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 =3D 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 =3D areq->iocb; > unsigned int resultlen; > > - lock_sock(sk); > - > /* Buffer size written by crypto operation. */ > resultlen =3D 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 aacae0837aff..db9378a45296 100644 > --- a/crypto/algif_aead.c > +++ b/crypto/algif_aead.c > @@ -268,12 +268,23 @@ static int _aead_recvmsg(struct socket *sock, struc= t msghdr *msg, > > if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) { > /* AIO operation */ > + sock_hold(sk); > areq->iocb =3D msg->msg_iocb; > aead_request_set_callback(&areq->cra_u.aead_req, > CRYPTO_TFM_REQ_MAY_BACKLOG, > af_alg_async_cb, areq); > err =3D ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_= req) : > crypto_aead_decrypt(&areq->cra_u.aead_re= q); > + > + /* AIO operation in progress */ > + if (err =3D=3D -EINPROGRESS || err =3D=3D -EBUSY) { > + /* Remember output size that will be generated. *= / > + areq->outlen =3D outlen; > + > + return -EIOCBQUEUED; > + } > + > + sock_put(sk); > } else { > /* Synchronous operation */ > aead_request_set_callback(&areq->cra_u.aead_req, > @@ -285,19 +296,9 @@ static int _aead_recvmsg(struct socket *sock, struct= msghdr *msg, > &ctx->wait); > } > > - /* AIO operation in progress */ > - if (err =3D=3D -EINPROGRESS) { > - sock_hold(sk); > - > - /* Remember output size that will be generated. */ > - areq->outlen =3D 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, str= uct msghdr *msg, > > if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) { > /* AIO operation */ > + sock_hold(sk); > areq->iocb =3D 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, st= ruct msghdr *msg, > err =3D ctx->enc ? > crypto_skcipher_encrypt(&areq->cra_u.skcipher_req= ) : > crypto_skcipher_decrypt(&areq->cra_u.skcipher_req= ); > + > + /* AIO operation in progress */ > + if (err =3D=3D -EINPROGRESS || err =3D=3D -EBUSY) { > + /* Remember output size that will be generated. *= / > + areq->outlen =3D 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, st= ruct msghdr *msg, > &ctx->wait); > } > > - /* AIO operation in progress */ > - if (err =3D=3D -EINPROGRESS) { > - sock_hold(sk); > - > - /* Remember output size that will be generated. */ > - areq->outlen =3D 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); > -- > 2.13.6 > >