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=-6.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 71193C433B4 for ; Tue, 11 May 2021 10:50:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B8EC61927 for ; Tue, 11 May 2021 10:50:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230343AbhEKKv2 (ORCPT ); Tue, 11 May 2021 06:51:28 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46586 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230237AbhEKKv2 (ORCPT ); Tue, 11 May 2021 06:51:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620730221; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=pDKfMCSmDrYbYLb3RYYkSWVBebsV7OFYV2lkS/seTjY=; b=X9q1DzlmW/HnYe7Icm34QGpe5i7YvcCha+iuozrJVUwNKwFBmX2DD8aSbOIoPrXhhGebQj dYosQe6Mw1DLGMbvYxLvOjZJEf6c0fqS0HBoGMz11xZcjCZW2WEhdgCpX2GSFlY/dH2WQ0 PklDF8B72XIEpw/8oFp6HQKRlUtIXFQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-235-k5-U_UGNPKSvNGkjgNC1IQ-1; Tue, 11 May 2021 06:50:19 -0400 X-MC-Unique: k5-U_UGNPKSvNGkjgNC1IQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 765F6107ACCA; Tue, 11 May 2021 10:50:17 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.3]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4E850189A5; Tue, 11 May 2021 10:50:15 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <1620467481-110575-1-git-send-email-yang.lee@linux.alibaba.com> References: <1620467481-110575-1-git-send-email-yang.lee@linux.alibaba.com> To: Yang Li Cc: dhowells@redhat.com, jarkko@kernel.org, jmorris@namei.org, serge@hallyn.com, nathan@kernel.org, ndesaulniers@google.com, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: Re: [PATCH] Keys: Remove redundant initialization of cred MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <2499882.1620730214.1@warthog.procyon.org.uk> Date: Tue, 11 May 2021 11:50:14 +0100 Message-ID: <2499883.1620730214@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org Yang Li wrote: > - const struct cred *cred = current_cred(); > + const struct cred *cred; Good catch, but it's probably the wrong fix. In that function, there is: const struct cred *cred = current_cred(); ... cred = get_current_cred(); keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred, ...); put_cred(cred); ... sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid)); ... So we get the creds again, but with a ref, and then drop after calling keyring_alloc()... and then access cred again, which is dodgy - but we get away with it because cred is still pinned by our task_struct. I think what is actually needed is to remove the get_current_cred() and the put_cred() calls, in which case, you want this: Fixes: d84f4f992cbd ("CRED: Inaugurate COW credentials") David