From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:22007 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389295AbgDMVwp (ORCPT ); Mon, 13 Apr 2020 17:52:45 -0400 Subject: Re: [PATCH 2/2] crypto: Remove unnecessary memzero_explicit() References: <20200413211550.8307-1-longman@redhat.com> <20200413211550.8307-3-longman@redhat.com> From: Waiman Long Message-ID: <7e13a94b-2e92-850f-33f7-0f42cfcd9009@redhat.com> Date: Mon, 13 Apr 2020 17:52:24 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-s390-owner@vger.kernel.org List-ID: To: Joe Perches , Andrew Morton , David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Linus Torvalds , Matthew Wilcox , David Rientjes Cc: linux-mm@kvack.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-crypto@vger.kernel.org, linux-s390@vger.kernel.org, linux-pm@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-mediatek@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-ppp@vger.kernel.org, wireguard@lists.zx2c4.com, linux-wireless@vger.kernel.org, devel@driverdev.osuosl.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-fscrypt@vger.kernel.org, ecryptfs@vger.kernel.org, kasan-dev@googlegroups.com, linux-bluetooth@vger.kernel.org, linux-wpan@vger.kernel.org, linux-sctp@vger.kernel.org, linux-nfs@vger.kernel.org, tipc-discussion@lists.sourceforge.net, cocci@systeme.lip6.fr, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org On 4/13/20 5:31 PM, Joe Perches wrote: > On Mon, 2020-04-13 at 17:15 -0400, Waiman Long wrote: >> Since kfree_sensitive() will do an implicit memzero_explicit(), there >> is no need to call memzero_explicit() before it. Eliminate those >> memzero_explicit() and simplify the call sites. > 2 bits of trivia: > >> diff --git a/drivers/crypto/allwinner/sun8i-ce/sun8i-ce-cipher.c b/drivers/crypto/allwinner/sun8i-ce/sun8i-ce-cipher.c > [] >> @@ -391,10 +388,7 @@ int sun8i_ce_aes_setkey(struct crypto_skcipher *tfm, const u8 *key, >> dev_dbg(ce->dev, "ERROR: Invalid keylen %u\n", keylen); >> return -EINVAL; >> } >> - if (op->key) { >> - memzero_explicit(op->key, op->keylen); >> - kfree(op->key); >> - } >> + kfree_sensitive(op->key); >> op->keylen = keylen; >> op->key = kmemdup(key, keylen, GFP_KERNEL | GFP_DMA); >> if (!op->key) > It might be a defect to set op->keylen before the kmemdup succeeds. It could be. I can move it down after the op->key check. >> @@ -416,10 +410,7 @@ int sun8i_ce_des3_setkey(struct crypto_skcipher *tfm, const u8 *key, >> if (err) >> return err; >> >> - if (op->key) { >> - memzero_explicit(op->key, op->keylen); >> - kfree(op->key); >> - } >> + free_sensitive(op->key, op->keylen); > Why not kfree_sensitive(op->key) ? Oh, it is a bug. I will send out v2 to fix that. Thanks for spotting it. Cheers, Longman > >