From nobody Mon Jun 30 14:21:24 2025 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4bW7d03Fhtz60XP1; Mon, 30 Jun 2025 14:21:24 +0000 (UTC) (envelope-from git@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 "R10" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4bW7d02S33z482F; Mon, 30 Jun 2025 14:21:24 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1751293284; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=IMXjFedC5hsMtHvPZCXlMuI722/a2KLSDQFDIuaRBk8=; b=mLCA8xLx5dfKnG+wQTpA+Be74Z3NwclACJsZ3gqLc4ctSSNMZ4oHxOyn/RL5lVeTLMUjw5 2FWc5ueNDqVRlsH1zaLW529Eh/zz8Ukl0YMzneDvEj+P6S7GYw1GtDFdUaMERe6GUQtRmf cvO/c3cdPavyD9OWEiBIiNiLwzK17ZKSn5v6wTyxTqYQyK+fXXKA7Kfele7mBVMJZpI3FK 4vXu8J6S16PWJRq0n7za4p6/3cklWsJknt8rwBx4tPB7fl2Mijw8P1EdCx1+zs529veoCy kEu3iUm6muuLztoE5I2YGepjT+tjMTLMyjUFCiPdHFf5KOrv555R5Y6YixRx3A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1751293284; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=IMXjFedC5hsMtHvPZCXlMuI722/a2KLSDQFDIuaRBk8=; b=m87XNWE4cG5m8nVL7qssMqhSEouIeLIUkat0brUsXBLngULd7sQItCknrdhhJdBxCwj7TB 7vcTFVEjMR9T/ja4tfXoS96PUxS7qMxXuEykd+2Tffo8d5Rs8OFJRu3boVSOdiVJGsBvKN a5WTbs7sJ4w1GNaJaGnWAyUVnh8cLDLRwdsKqg6VXfsvTXNCJWx0GylepDMNyKkWjYiJox yN0Pfr5X3T0Tno6cKXxe3HoAqsWyDzOVst7NZ1Vf9aMEEnAMA26PYrKqjZRKFFHQI3ZgKo PisSzGH4IVxkINomcVWNP0xTh2gb36nSS2U7uLANi/AE48srctWepXRrjqH26g== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1751293284; a=rsa-sha256; cv=none; b=R7gwVbfGdi7ac0ISxz1DvkWZfoy92TD1leGdZaV4ngacdPWfmmi5KV/yvjs0aomUvUMdzL WwLL3PtleK5LI2s217DJrGvWP/Tkh7GVW/t50++Bi3ZAIuHtksb+x9Nq5H7/JeaJ3NFKr9 a4j74aDQ2oQI7vd1R7T7qiUSsb+1UyOC/wdaDGlltFu2UA+7P6a/kmhvytC5Oax1e3IaES I/QkFN9L4nfrBpQ/47iyROuGnpdlpLOxRU1SHYqu33pgAWcd/8MtHWnhFrbCBWpFLHptmS Hbn/u7ntUHXsndLvTfhQ3sHDkH0uvF0hUMlrVaS6J0lUG7rO+UlIb4f0CIl1yw== Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (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 did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4bW7d01sbdz178H; Mon, 30 Jun 2025 14:21:24 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.18.1/8.18.1) with ESMTP id 55UELOoW074995; Mon, 30 Jun 2025 14:21:24 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.18.1/8.18.1/Submit) id 55UELOH2074992; Mon, 30 Jun 2025 14:21:24 GMT (envelope-from git) Date: Mon, 30 Jun 2025 14:21:24 GMT Message-Id: <202506301421.55UELOH2074992@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: Mark Johnston Subject: git: 3feafab4a34c - stable/14 - namei: Make stackable filesystems check harder for jail roots List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: markj X-Git-Repository: src X-Git-Refname: refs/heads/stable/14 X-Git-Reftype: branch X-Git-Commit: 3feafab4a34c95209cd4fc3e6224c324efc056f3 Auto-Submitted: auto-generated The branch stable/14 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=3feafab4a34c95209cd4fc3e6224c324efc056f3 commit 3feafab4a34c95209cd4fc3e6224c324efc056f3 Author: Mark Johnston AuthorDate: 2025-05-23 12:52:24 +0000 Commit: Mark Johnston CommitDate: 2025-06-30 14:19:30 +0000 namei: Make stackable filesystems check harder for jail roots Suppose a process has its cwd pointing to a nullfs directory, where the lower directory is also visible in the jail's filesystem namespace. Suppose that the lower directory vnode is moved out from under the nullfs mount. The nullfs vnode still shadows the lower vnode, and dotdot lookups relative to that directory will instantiate new nullfs vnodes outside of the nullfs mountpoint, effectively shadowing the lower filesystem. This phenomenon can be abused to escape a chroot, since the nullfs vnodes instantiated by these dotdot lookups defeat the root vnode check in vfs_lookup(), which uses vnode pointer equality to test for the process root. Fix this by extending nullfs and unionfs to perform the same check, exploiting the fact that the passed componentname is embedded in a nameidata structure to avoid changing the VOP_LOOKUP interface. That is, add a flag to indicate that containerof can be used to get the full nameidata structure, and perform the root vnode check on the lower vnode when performing a dotdot lookup. PR: 262180 Reviewed by: olce, kib MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D50418 (cherry picked from commit 7587f6d4840f8d363e457cddc14c184cf1fe7cc1) --- sys/fs/nullfs/null_vnops.c | 28 ++++++++++++++++++---------- sys/fs/unionfs/union_vnops.c | 21 +++++++++++++++++++++ sys/kern/vfs_cache.c | 11 +---------- sys/kern/vfs_lookup.c | 41 ++++++++++++++++++++++++++++++----------- sys/sys/namei.h | 5 ++++- 5 files changed, 74 insertions(+), 32 deletions(-) diff --git a/sys/fs/nullfs/null_vnops.c b/sys/fs/nullfs/null_vnops.c index f2c426d41f61..41915da7f13c 100644 --- a/sys/fs/nullfs/null_vnops.c +++ b/sys/fs/nullfs/null_vnops.c @@ -407,17 +407,25 @@ null_lookup(struct vop_lookup_args *ap) /* * Renames in the lower mounts might create an inconsistent - * configuration where lower vnode is moved out of the - * directory tree remounted by our null mount. Do not try to - * handle it fancy, just avoid VOP_LOOKUP() with DOTDOT name - * which cannot be handled by VOP, at least passing over lower - * root. + * configuration where lower vnode is moved out of the directory tree + * remounted by our null mount. + * + * Do not try to handle it fancy, just avoid VOP_LOOKUP() with DOTDOT + * name which cannot be handled by the VOP. */ - if ((ldvp->v_vflag & VV_ROOT) != 0 && (flags & ISDOTDOT) != 0) { - KASSERT((dvp->v_vflag & VV_ROOT) == 0, - ("ldvp %p fl %#x dvp %p fl %#x flags %#jx", - ldvp, ldvp->v_vflag, dvp, dvp->v_vflag, (uintmax_t)flags)); - return (ENOENT); + if ((flags & ISDOTDOT) != 0) { + struct nameidata *ndp; + + if ((ldvp->v_vflag & VV_ROOT) != 0) { + KASSERT((dvp->v_vflag & VV_ROOT) == 0, + ("ldvp %p fl %#x dvp %p fl %#x flags %#jx", + ldvp, ldvp->v_vflag, dvp, dvp->v_vflag, + (uintmax_t)flags)); + return (ENOENT); + } + ndp = vfs_lookup_nameidata(cnp); + if (ndp != NULL && vfs_lookup_isroot(ndp, ldvp)) + return (ENOENT); } /* diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c index 7618e2575819..01378b06ba55 100644 --- a/sys/fs/unionfs/union_vnops.c +++ b/sys/fs/unionfs/union_vnops.c @@ -78,6 +78,21 @@ VNASSERT(((vp)->v_op == &unionfs_vnodeops), vp, \ ("%s: non-unionfs vnode", __func__)) +static bool +unionfs_lookup_isroot(struct componentname *cnp, struct vnode *dvp) +{ + struct nameidata *ndp; + + if (dvp == NULL) + return (false); + if ((dvp->v_vflag & VV_ROOT) != 0) + return (true); + ndp = vfs_lookup_nameidata(cnp); + if (ndp == NULL) + return (false); + return (vfs_lookup_isroot(ndp, dvp)); +} + static int unionfs_lookup(struct vop_cachedlookup_args *ap) { @@ -128,6 +143,12 @@ unionfs_lookup(struct vop_cachedlookup_args *ap) if (LOOKUP != nameiop && udvp == NULLVP) return (EROFS); + if (unionfs_lookup_isroot(cnp, udvp) || + unionfs_lookup_isroot(cnp, ldvp)) { + error = ENOENT; + goto unionfs_lookup_return; + } + if (udvp != NULLVP) { dtmpvp = udvp; if (ldvp != NULLVP) diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index e25efe2986b2..2c2e18640a76 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -5185,7 +5185,6 @@ cache_fplookup_dotdot(struct cache_fpl *fpl) struct componentname *cnp; struct namecache *ncp; struct vnode *dvp; - struct prison *pr; u_char nc_flag; ndp = fpl->ndp; @@ -5197,15 +5196,7 @@ cache_fplookup_dotdot(struct cache_fpl *fpl) /* * XXX this is racy the same way regular lookup is */ - for (pr = cnp->cn_cred->cr_prison; pr != NULL; - pr = pr->pr_parent) - if (dvp == pr->pr_root) - break; - - if (dvp == ndp->ni_rootdir || - dvp == ndp->ni_topdir || - dvp == rootvnode || - pr != NULL) { + if (vfs_lookup_isroot(ndp, dvp)) { fpl->tvp = dvp; fpl->tvp_seqc = vn_seqc_read_any(dvp); if (seqc_in_modify(fpl->tvp_seqc)) { diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c index b7f751a364ce..1d303fecf493 100644 --- a/sys/kern/vfs_lookup.c +++ b/sys/kern/vfs_lookup.c @@ -612,12 +612,12 @@ namei(struct nameidata *ndp) } #endif ndp->ni_cnd.cn_cred = td->td_ucred; - KASSERT(ndp->ni_resflags == 0, ("%s: garbage in ni_resflags: %x\n", + KASSERT(ndp->ni_resflags == 0, ("%s: garbage in ni_resflags: %x", __func__, ndp->ni_resflags)); KASSERT(cnp->cn_cred && td->td_proc, ("namei: bad cred/proc")); KASSERT((cnp->cn_flags & NAMEI_INTERNAL_FLAGS) == 0, - ("namei: unexpected flags: %" PRIx64 "\n", - cnp->cn_flags & NAMEI_INTERNAL_FLAGS)); + ("namei: unexpected flags: %#jx", + (uintmax_t)(cnp->cn_flags & NAMEI_INTERNAL_FLAGS))); if (cnp->cn_flags & NOCACHE) KASSERT(cnp->cn_nameiop != LOOKUP, ("%s: NOCACHE passed with LOOKUP", __func__)); @@ -863,6 +863,30 @@ bad: return (error); } +struct nameidata * +vfs_lookup_nameidata(struct componentname *cnp) +{ + if ((cnp->cn_flags & NAMEILOOKUP) == 0) + return (NULL); + return (__containerof(cnp, struct nameidata, ni_cnd)); +} + +/* + * Would a dotdot lookup relative to dvp cause this lookup to cross a jail or + * chroot boundary? + */ +bool +vfs_lookup_isroot(struct nameidata *ndp, struct vnode *dvp) +{ + for (struct prison *pr = ndp->ni_cnd.cn_cred->cr_prison; pr != NULL; + pr = pr->pr_parent) { + if (dvp == pr->pr_root) + return (true); + } + return (dvp == ndp->ni_rootdir || dvp == ndp->ni_topdir || + dvp == rootvnode); +} + /* * FAILIFEXISTS handling. * @@ -1021,7 +1045,6 @@ vfs_lookup(struct nameidata *ndp) char *lastchar; /* location of the last character */ struct vnode *dp = NULL; /* the directory we are searching */ struct vnode *tdp; /* saved dp */ - struct prison *pr; size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */ int docache; /* == 0 do not cache last component */ int wantparent; /* 1 => wantparent or lockparent flag */ @@ -1207,13 +1230,9 @@ dirloop: goto bad; } for (;;) { - for (pr = cnp->cn_cred->cr_prison; pr != NULL; - pr = pr->pr_parent) - if (dp == pr->pr_root) - break; - bool isroot = dp == ndp->ni_rootdir || - dp == ndp->ni_topdir || dp == rootvnode || - pr != NULL; + bool isroot; + + isroot = vfs_lookup_isroot(ndp, dp); if (__predict_false(isroot && (ndp->ni_lcf & (NI_LCF_STRICTREL | NI_LCF_STRICTREL_KTR)) != 0)) { if ((ndp->ni_lcf & NI_LCF_STRICTREL_KTR) != 0) diff --git a/sys/sys/namei.h b/sys/sys/namei.h index 3db7b8e13749..5e9a5bf4a699 100644 --- a/sys/sys/namei.h +++ b/sys/sys/namei.h @@ -152,6 +152,7 @@ int cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status, #define LOCKSHARED 0x0100 /* Shared lock leaf */ #define NOFOLLOW 0x0000 /* do not follow symbolic links (pseudo) */ #define RBENEATH 0x100000000ULL /* No escape, even tmp, from start dir */ +#define NAMEILOOKUP 0x200000000ULL /* cnp is embedded in nameidata */ #define MODMASK 0xf000001ffULL /* mask of operational modifiers */ /* @@ -248,7 +249,7 @@ do { \ NDINIT_PREFILL(_ndp); \ NDINIT_DBG(_ndp); \ _ndp->ni_cnd.cn_nameiop = op; \ - _ndp->ni_cnd.cn_flags = flags; \ + _ndp->ni_cnd.cn_flags = (flags) | NAMEILOOKUP; \ _ndp->ni_segflg = segflg; \ _ndp->ni_dirp = namep; \ _ndp->ni_dirfd = dirfd; \ @@ -285,6 +286,8 @@ do { \ int namei(struct nameidata *ndp); int vfs_lookup(struct nameidata *ndp); +bool vfs_lookup_isroot(struct nameidata *ndp, struct vnode *dvp); +struct nameidata *vfs_lookup_nameidata(struct componentname *cnp); int vfs_relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, bool refstart);