From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1556C10F13 for ; Thu, 11 Apr 2019 21:37:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB6402146F for ; Thu, 11 Apr 2019 21:37:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1555018633; bh=bn6HbNIYb15cSziCnV40SnoGAC5PNXU+KimMnZ/Tq28=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=indq7XcIzGLN6j+/dhda+NlQ32Abbqy1oYqOqc0hC/F/ct0oMnRcJViJW9oCGUU87 f/CNJ9Ol0T1Ui5geVxPjfZqaM/rjFacZ+R+Ch7oiHHMk93dtUnPGpP9mFSUUaBe4l2 h6N4epSqjydxWb4ggwGVfvSq9YmkamwdzGAQWnKI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726794AbfDKVhN (ORCPT ); Thu, 11 Apr 2019 17:37:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:32816 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726655AbfDKVhN (ORCPT ); Thu, 11 Apr 2019 17:37:13 -0400 Received: from gmail.com (unknown [104.132.1.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 50E6D2146F; Thu, 11 Apr 2019 21:37:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1555018632; bh=bn6HbNIYb15cSziCnV40SnoGAC5PNXU+KimMnZ/Tq28=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=IXectrpOaqlzGo40o3aspa7x9UitGC8MUjKnHDIMQdAp6QAigxpQTjMzSxDxa0LxE LtnwvGByl1GxDwOYfE+uMNyaanYKe32jFZM+VLXZtNaUXTWCLxdaoBhpUOKuMkZgL4 xnbNku2wLLo+1Vaa0C3sd/x6gPIEVOeAzNA8s0fo= Date: Thu, 11 Apr 2019 14:37:10 -0700 From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] fscrypt: add memory barrier when loading essiv_hash_tfm Message-ID: <20190411213710.GF225654@gmail.com> References: <20190318172454.240412-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190318172454.240412-1-ebiggers@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Mar 18, 2019 at 10:24:54AM -0700, Eric Biggers wrote: > From: Eric Biggers > > Load 'essiv_hash_tfm' using smp_load_acquire() to guarantee that the > struct crypto_shash is seen as fully initialized before being used. > > Signed-off-by: Eric Biggers > --- > fs/crypto/keyinfo.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c > index ba74dafa18a3..d1f0f8369d51 100644 > --- a/fs/crypto/keyinfo.c > +++ b/fs/crypto/keyinfo.c > @@ -379,7 +379,7 @@ fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode, > > static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) > { > - struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); > + struct crypto_shash *tfm = smp_load_acquire(&essiv_hash_tfm); > > /* init hash transform on demand */ > if (unlikely(!tfm)) { > -- > 2.21.0.225.g810b269d1ac-goog > Actually I think we only need a data dependency barrier here, so this patch isn't needed. See discussion of similar case at https://marc.info/?l=linux-fsdevel&m=155487269904655&w=2 - Eric