Return-Path: Received: from orcrist.hmeau.com ([104.223.48.154]:42740 "EHLO deadmen.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726556AbeKWBYZ (ORCPT ); Thu, 22 Nov 2018 20:24:25 -0500 Date: Thu, 22 Nov 2018 22:44:41 +0800 From: Herbert Xu To: Pan Bian Cc: "David S. Miller" , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] crypto: do not free algorithm before using Message-ID: <20181122144441.tkfmrq3lzibq2g3y@gondor.apana.org.au> References: <1542880816-63838-1-git-send-email-bianpan2016@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1542880816-63838-1-git-send-email-bianpan2016@163.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Thu, Nov 22, 2018 at 06:00:16PM +0800, Pan Bian wrote: > In multiple functions, the algorithm fields are read after its reference > is dropped through crypto_mod_put. In this case, the algorithm memory > may be freed, resulting in use-after-free bugs. This patch delays the > put operation until the algorithm is never used. > > Signed-off-by: Pan Bian I don't think this patch is needed. > --- > crypto/cbc.c | 6 ++++-- > crypto/cfb.c | 6 ++++-- > crypto/pcbc.c | 6 ++++-- > 3 files changed, 12 insertions(+), 6 deletions(-) > > diff --git a/crypto/cbc.c b/crypto/cbc.c > index b761b1f..dd5f332 100644 > --- a/crypto/cbc.c > +++ b/crypto/cbc.c > @@ -140,9 +140,8 @@ static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb) > spawn = skcipher_instance_ctx(inst); > err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst), > CRYPTO_ALG_TYPE_MASK); > - crypto_mod_put(alg); > if (err) > - goto err_free_inst; > + goto err_put_alg; We can safely drop the reference to the algorithm because the spawn is now meant to hold a reference to it. As long as the spawn is alive so will the algorithm. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt