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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 B031DC3B1A1 for ; Fri, 14 Feb 2020 17:11:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 825A520656 for ; Fri, 14 Feb 2020 17:11:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581700267; bh=nfuiEToh8iAo7zF9jE6osmZpRN7Rd4q3isqck//PNyo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2Z261t/s84661ymGuD2ebjcz0/m+uMSlLnnw98hP6RKcm/SXjpbCOQiXYrj46aZ+d 66ZyT2Bn+/UQsHAttCr9Enf76SPCjWMb4CQMaIoJPVMqYR7h9x0LfOMIT31tP9yWX/ iupRP/g87WtsstXg6Wj/606H0LtWRn15jez0V2zE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392174AbgBNQNc (ORCPT ); Fri, 14 Feb 2020 11:13:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:42084 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390336AbgBNQNb (ORCPT ); Fri, 14 Feb 2020 11:13:31 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 79D8E246AA; Fri, 14 Feb 2020 16:13:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581696810; bh=nfuiEToh8iAo7zF9jE6osmZpRN7Rd4q3isqck//PNyo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hCgnW7EJ4156JMOet7Z/baVSke9tK/RBdw20iIxVjNnMNapJyVogi6+coH1b1W9f6 YUmd5MzU8KU25ETQE45b2qw492kTz60qju2n5s7G6XKIl8DtZHuVFnEKkqWutvOBRN pQeiAlmJL/MhN/6prYDxWk1pzvIDATx+7vUGhl3w= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Stephen Smalley , Will Deacon , Al Viro , Paul Moore , Sasha Levin , selinux@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 080/252] selinux: fall back to ref-walk if audit is required Date: Fri, 14 Feb 2020 11:08:55 -0500 Message-Id: <20200214161147.15842-80-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200214161147.15842-1-sashal@kernel.org> References: <20200214161147.15842-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Stephen Smalley [ Upstream commit 0188d5c025ca8fe756ba3193bd7d150139af5a88 ] commit bda0be7ad994 ("security: make inode_follow_link RCU-walk aware") passed down the rcu flag to the SELinux AVC, but failed to adjust the test in slow_avc_audit() to also return -ECHILD on LSM_AUDIT_DATA_DENTRY. Previously, we only returned -ECHILD if generating an audit record with LSM_AUDIT_DATA_INODE since this was only relevant from inode_permission. Move the handling of MAY_NOT_BLOCK to avc_audit() and its inlined equivalent in selinux_inode_permission() immediately after we determine that audit is required, and always fall back to ref-walk in this case. Fixes: bda0be7ad994 ("security: make inode_follow_link RCU-walk aware") Reported-by: Will Deacon Suggested-by: Al Viro Signed-off-by: Stephen Smalley Signed-off-by: Paul Moore Signed-off-by: Sasha Levin --- security/selinux/avc.c | 24 +++++------------------- security/selinux/hooks.c | 11 +++++++---- security/selinux/include/avc.h | 8 +++++--- 3 files changed, 17 insertions(+), 26 deletions(-) diff --git a/security/selinux/avc.c b/security/selinux/avc.c index 5de18a6d5c3f0..0622cae510461 100644 --- a/security/selinux/avc.c +++ b/security/selinux/avc.c @@ -496,7 +496,7 @@ static inline int avc_xperms_audit(struct selinux_state *state, if (likely(!audited)) return 0; return slow_avc_audit(state, ssid, tsid, tclass, requested, - audited, denied, result, ad, 0); + audited, denied, result, ad); } static void avc_node_free(struct rcu_head *rhead) @@ -766,8 +766,7 @@ static void avc_audit_post_callback(struct audit_buffer *ab, void *a) noinline int slow_avc_audit(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass, u32 requested, u32 audited, u32 denied, int result, - struct common_audit_data *a, - unsigned int flags) + struct common_audit_data *a) { struct common_audit_data stack_data; struct selinux_audit_data sad; @@ -777,17 +776,6 @@ noinline int slow_avc_audit(struct selinux_state *state, a->type = LSM_AUDIT_DATA_NONE; } - /* - * When in a RCU walk do the audit on the RCU retry. This is because - * the collection of the dname in an inode audit message is not RCU - * safe. Note this may drop some audits when the situation changes - * during retry. However this is logically just as if the operation - * happened a little later. - */ - if ((a->type == LSM_AUDIT_DATA_INODE) && - (flags & MAY_NOT_BLOCK)) - return -ECHILD; - sad.tclass = tclass; sad.requested = requested; sad.ssid = ssid; @@ -860,16 +848,14 @@ static int avc_update_node(struct selinux_avc *avc, /* * If we are in a non-blocking code path, e.g. VFS RCU walk, * then we must not add permissions to a cache entry - * because we cannot safely audit the denial. Otherwise, + * because we will not audit the denial. Otherwise, * during the subsequent blocking retry (e.g. VFS ref walk), we * will find the permissions already granted in the cache entry * and won't audit anything at all, leading to silent denials in * permissive mode that only appear when in enforcing mode. * - * See the corresponding handling in slow_avc_audit(), and the - * logic in selinux_inode_follow_link and selinux_inode_permission - * for the VFS MAY_NOT_BLOCK flag, which is transliterated into - * AVC_NONBLOCKING for avc_has_perm_noaudit(). + * See the corresponding handling of MAY_NOT_BLOCK in avc_audit() + * and selinux_inode_permission(). */ if (flags & AVC_NONBLOCKING) return 0; diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 040c843968dc6..c574285966f9d 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3171,8 +3171,7 @@ static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode, static noinline int audit_inode_permission(struct inode *inode, u32 perms, u32 audited, u32 denied, - int result, - unsigned flags) + int result) { struct common_audit_data ad; struct inode_security_struct *isec = inode->i_security; @@ -3183,7 +3182,7 @@ static noinline int audit_inode_permission(struct inode *inode, rc = slow_avc_audit(&selinux_state, current_sid(), isec->sid, isec->sclass, perms, - audited, denied, result, &ad, flags); + audited, denied, result, &ad); if (rc) return rc; return 0; @@ -3230,7 +3229,11 @@ static int selinux_inode_permission(struct inode *inode, int mask) if (likely(!audited)) return rc; - rc2 = audit_inode_permission(inode, perms, audited, denied, rc, flags); + /* fall back to ref-walk if we have to generate audit */ + if (flags & MAY_NOT_BLOCK) + return -ECHILD; + + rc2 = audit_inode_permission(inode, perms, audited, denied, rc); if (rc2) return rc2; return rc; diff --git a/security/selinux/include/avc.h b/security/selinux/include/avc.h index 74ea50977c201..cf4cc3ef959b5 100644 --- a/security/selinux/include/avc.h +++ b/security/selinux/include/avc.h @@ -100,8 +100,7 @@ static inline u32 avc_audit_required(u32 requested, int slow_avc_audit(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass, u32 requested, u32 audited, u32 denied, int result, - struct common_audit_data *a, - unsigned flags); + struct common_audit_data *a); /** * avc_audit - Audit the granting or denial of permissions. @@ -135,9 +134,12 @@ static inline int avc_audit(struct selinux_state *state, audited = avc_audit_required(requested, avd, result, 0, &denied); if (likely(!audited)) return 0; + /* fall back to ref-walk if we have to generate audit */ + if (flags & MAY_NOT_BLOCK) + return -ECHILD; return slow_avc_audit(state, ssid, tsid, tclass, requested, audited, denied, result, - a, flags); + a); } #define AVC_STRICT 1 /* Ignore permissive mode. */ -- 2.20.1