From owner-svn-src-head@freebsd.org Tue Aug 25 14:18:51 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 7AD483CCE34; Tue, 25 Aug 2020 14:18:51 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4BbWLz2hdzz4TkK; Tue, 25 Aug 2020 14:18:51 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 40D472ADD2; Tue, 25 Aug 2020 14:18:51 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 07PEIpPn086227; Tue, 25 Aug 2020 14:18:51 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 07PEIoBB086223; Tue, 25 Aug 2020 14:18:50 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <202008251418.07PEIoBB086223@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Tue, 25 Aug 2020 14:18:50 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r364769 - in head/sys: kern sys X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: in head/sys: kern sys X-SVN-Commit-Revision: 364769 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Aug 2020 14:18:51 -0000 Author: mjg Date: Tue Aug 25 14:18:50 2020 New Revision: 364769 URL: https://svnweb.freebsd.org/changeset/base/364769 Log: vfs: respect PRIV_VFS_LOOKUP in vaccess_smr Reported by: novel Modified: head/sys/kern/kern_jail.c head/sys/kern/kern_priv.c head/sys/kern/vfs_subr.c head/sys/sys/priv.h Modified: head/sys/kern/kern_jail.c ============================================================================== --- head/sys/kern/kern_jail.c Tue Aug 25 13:45:06 2020 (r364768) +++ head/sys/kern/kern_jail.c Tue Aug 25 14:18:50 2020 (r364769) @@ -3049,6 +3049,7 @@ prison_priv_check(struct ucred *cred, int priv) * called for them. See priv_check_cred(). */ switch (priv) { + case PRIV_VFS_LOOKUP: case PRIV_VFS_GENERATION: KASSERT(0, ("prison_priv_check instead of a custom handler " "called for %d\n", priv)); @@ -3277,7 +3278,6 @@ prison_priv_check(struct ucred *cred, int priv) case PRIV_VFS_WRITE: case PRIV_VFS_ADMIN: case PRIV_VFS_EXEC: - case PRIV_VFS_LOOKUP: case PRIV_VFS_BLOCKRESERVE: /* XXXRW: Slightly surprising. */ case PRIV_VFS_CHFLAGS_DEV: case PRIV_VFS_CHOWN: Modified: head/sys/kern/kern_priv.c ============================================================================== --- head/sys/kern/kern_priv.c Tue Aug 25 13:45:06 2020 (r364768) +++ head/sys/kern/kern_priv.c Tue Aug 25 14:18:50 2020 (r364769) @@ -129,6 +129,8 @@ priv_check_cred(struct ucred *cred, int priv) priv)); switch (priv) { + case PRIV_VFS_LOOKUP: + return (priv_check_cred_vfs_lookup(cred)); case PRIV_VFS_GENERATION: return (priv_check_cred_vfs_generation(cred)); } @@ -245,6 +247,56 @@ priv_check(struct thread *td, int priv) KASSERT(td == curthread, ("priv_check: td != curthread")); return (priv_check_cred(td->td_ucred, priv)); +} + +static int __noinline +priv_check_cred_vfs_lookup_slow(struct ucred *cred) +{ + int error; + + error = priv_check_cred_pre(cred, PRIV_VFS_LOOKUP); + if (error) + goto out; + + if (cred->cr_uid == 0 && suser_enabled) { + error = 0; + goto out; + } + + return (priv_check_cred_post(cred, PRIV_VFS_LOOKUP, error, false)); +out: + return (priv_check_cred_post(cred, PRIV_VFS_LOOKUP, error, true)); + +} + +int +priv_check_cred_vfs_lookup(struct ucred *cred) +{ + int error; + + if (__predict_false(mac_priv_check_fp_flag || + mac_priv_grant_fp_flag || SDT_PROBES_ENABLED())) + return (priv_check_cred_vfs_lookup_slow(cred)); + + error = EPERM; + if (cred->cr_uid == 0 && suser_enabled) + error = 0; + return (error); +} + +int +priv_check_cred_vfs_lookup_nomac(struct ucred *cred) +{ + int error; + + if (__predict_false(mac_priv_check_fp_flag || + mac_priv_grant_fp_flag || SDT_PROBES_ENABLED())) + return (EAGAIN); + + error = EPERM; + if (cred->cr_uid == 0 && suser_enabled) + error = 0; + return (error); } static int __noinline Modified: head/sys/kern/vfs_subr.c ============================================================================== --- head/sys/kern/vfs_subr.c Tue Aug 25 13:45:06 2020 (r364768) +++ head/sys/kern/vfs_subr.c Tue Aug 25 14:18:50 2020 (r364769) @@ -5045,6 +5045,7 @@ vn_isdisk(struct vnode *vp) int vaccess_vexec_smr(mode_t file_mode, uid_t file_uid, gid_t file_gid, struct ucred *cred) { + int error; VFS_SMR_ASSERT_ENTERED(); @@ -5067,7 +5068,9 @@ vaccess_vexec_smr(mode_t file_mode, uid_t file_uid, gi return (0); out_error: /* - * Permission check failed. + * Permission check failed, but it is possible denial will get overwritten + * (e.g., when root is traversing through a 700 directory owned by someone + * else). * * vaccess() calls priv_check_cred which in turn can descent into MAC * modules overriding this result. It's quite unclear what semantics @@ -5075,9 +5078,20 @@ out_error: * from within the SMR section. This also means if any such modules * are present, we have to let the regular lookup decide. */ - if (__predict_false(mac_priv_check_fp_flag || mac_priv_grant_fp_flag)) + error = priv_check_cred_vfs_lookup_nomac(cred); + switch (error) { + case 0: + return (0); + case EAGAIN: + /* + * MAC modules present. + */ return (EAGAIN); - return (EACCES); + case EPERM: + return (EACCES); + default: + return (error); + } } /* Modified: head/sys/sys/priv.h ============================================================================== --- head/sys/sys/priv.h Tue Aug 25 13:45:06 2020 (r364768) +++ head/sys/sys/priv.h Tue Aug 25 14:18:50 2020 (r364769) @@ -536,6 +536,8 @@ struct thread; struct ucred; int priv_check(struct thread *td, int priv); int priv_check_cred(struct ucred *cred, int priv); +int priv_check_cred_vfs_lookup(struct ucred *cred); +int priv_check_cred_vfs_lookup_nomac(struct ucred *cred); int priv_check_cred_vfs_generation(struct ucred *cred); #endif