From owner-dev-commits-src-main@freebsd.org Mon Dec 28 21:39:33 2020 Return-Path: Delivered-To: dev-commits-src-main@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 A778E4C223E; Mon, 28 Dec 2020 21:39:33 +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 "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4D4WCn4DdVz4m8V; Mon, 28 Dec 2020 21:39:33 +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 8438E2080C; Mon, 28 Dec 2020 21:39:33 +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 0BSLdXlI083087; Mon, 28 Dec 2020 21:39:33 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 0BSLdXRR083086; Mon, 28 Dec 2020 21:39:33 GMT (envelope-from git) Date: Mon, 28 Dec 2020 21:39:33 GMT Message-Id: <202012282139.0BSLdXRR083086@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Mateusz Guzik Subject: git: 0c09f4b0cc63 - main - cache: work around corner case of dvp == tvp in cache_fplookup_final_modifying MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: mjg X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 0c09f4b0cc633750a3cbf724e8590ed9d4ef92e1 Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-main@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: "Commit messages for the main branch of the src repository." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Dec 2020 21:39:33 -0000 The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=0c09f4b0cc633750a3cbf724e8590ed9d4ef92e1 commit 0c09f4b0cc633750a3cbf724e8590ed9d4ef92e1 Author: Mateusz Guzik AuthorDate: 2020-12-28 21:24:53 +0000 Commit: Mateusz Guzik CommitDate: 2020-12-28 21:38:20 +0000 cache: work around corner case of dvp == tvp in cache_fplookup_final_modifying Fixes a panic where the kernel would unlock an unheld lock coming from rename looking up "foo/." as the source. Reported by: markj (syzkaller) --- sys/kern/vfs_cache.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index 4513e4dc970f..94d622867425 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -4063,6 +4063,19 @@ cache_fplookup_final_modifying(struct cache_fpl *fpl) return (cache_fpl_handled(fpl, 0)); } + /* + * There are very hairy corner cases concerning various flag combinations + * and locking state. In particular here we only hold one lock instead of + * two. + * + * Skip the complexity as it is of no significance for normal workloads. + */ + if (__predict_false(tvp == dvp)) { + vput(dvp); + vrele(tvp); + return (cache_fpl_aborted(fpl)); + } + /* * Check if the target is either a symlink or a mount point. * Since we expect this to be the terminal vnode it should