From owner-dev-commits-src-all@freebsd.org Tue Aug 3 09:52:47 2021 Return-Path: Delivered-To: dev-commits-src-all@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 6EBC2634A66; Tue, 3 Aug 2021 09:52:47 +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 "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4Gf9Cg0Pwsz3NgK; Tue, 3 Aug 2021 09:52:47 +0000 (UTC) (envelope-from git@FreeBSD.org) 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 D3D8811607; Tue, 3 Aug 2021 09:52:46 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 1739qk7Y081334; Tue, 3 Aug 2021 09:52:46 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 1739qkUc081333; Tue, 3 Aug 2021 09:52:46 GMT (envelope-from git) Date: Tue, 3 Aug 2021 09:52:46 GMT Message-Id: <202108030952.1739qkUc081333@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: Konstantin Belousov Subject: git: 0a4eb4d65c11 - stable/13 - null_bypass(): prevent loosing the only reference to the lower vnode MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: kib X-Git-Repository: src X-Git-Refname: refs/heads/stable/13 X-Git-Reftype: branch X-Git-Commit: 0a4eb4d65c11dc775733dd5a0a470419e1376515 Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-all@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for all branches of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 Aug 2021 09:52:47 -0000 The branch stable/13 has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=0a4eb4d65c11dc775733dd5a0a470419e1376515 commit 0a4eb4d65c11dc775733dd5a0a470419e1376515 Author: Konstantin Belousov AuthorDate: 2021-07-20 00:53:08 +0000 Commit: Konstantin Belousov CommitDate: 2021-08-03 09:52:35 +0000 null_bypass(): prevent loosing the only reference to the lower vnode (cherry picked from commit d5b078163e0d6bb2fe36f8e49a44853908d5e2db) --- sys/fs/nullfs/null_vnops.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff --git a/sys/fs/nullfs/null_vnops.c b/sys/fs/nullfs/null_vnops.c index 4dfc5efaf9ed..03f8b0dcbf7d 100644 --- a/sys/fs/nullfs/null_vnops.c +++ b/sys/fs/nullfs/null_vnops.c @@ -266,6 +266,17 @@ null_bypass(struct vop_generic_args *ap) old_vps[i] = *this_vp_p; *(vps_p[i]) = NULLVPTOLOWERVP(*this_vp_p); + /* + * The upper vnode reference to the lower + * vnode is the only reference that keeps our + * pointer to the lower vnode alive. If lower + * vnode is relocked during the VOP call, + * upper vnode might become unlocked and + * reclaimed, which invalidates our reference. + * Add a transient hold around VOP call. + */ + vhold(*this_vp_p); + /* * XXX - Several operations have the side effect * of vrele'ing their vp's. We must account for @@ -300,6 +311,7 @@ null_bypass(struct vop_generic_args *ap) lvp = *(vps_p[i]); /* + * Get rid of the transient hold on lvp. * If lowervp was unlocked during VOP * operation, nullfs upper vnode could have * been reclaimed, which changes its v_vnlock @@ -307,11 +319,14 @@ null_bypass(struct vop_generic_args *ap) * must move lock ownership from lower to * upper (reclaimed) vnode. */ - if (lvp != NULLVP && - VOP_ISLOCKED(lvp) == LK_EXCLUSIVE && - old_vps[i]->v_vnlock != lvp->v_vnlock) { - VOP_UNLOCK(lvp); - VOP_LOCK(old_vps[i], LK_EXCLUSIVE | LK_RETRY); + if (lvp != NULLVP) { + if (VOP_ISLOCKED(lvp) == LK_EXCLUSIVE && + old_vps[i]->v_vnlock != lvp->v_vnlock) { + VOP_UNLOCK(lvp); + VOP_LOCK(old_vps[i], LK_EXCLUSIVE | + LK_RETRY); + } + vdrop(lvp); } *(vps_p[i]) = old_vps[i];