From owner-dev-commits-src-branches@freebsd.org Tue Apr 6 19:18:15 2021 Return-Path: Delivered-To: dev-commits-src-branches@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 B0E515B50D8; Tue, 6 Apr 2021 19:18:15 +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 4FFHP32SDQz4cDn; Tue, 6 Apr 2021 19:18:15 +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 701DC11B97; Tue, 6 Apr 2021 19:18:13 +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 136JIDJg097128; Tue, 6 Apr 2021 19:18:13 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 136JIDS2097127; Tue, 6 Apr 2021 19:18:13 GMT (envelope-from git) Date: Tue, 6 Apr 2021 19:18:13 GMT Message-Id: <202104061918.136JIDS2097127@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: 2e08308d62f3 - stable/13 - vm_fault: Shoot down multiply mapped COW source page mappings 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/13 X-Git-Reftype: branch X-Git-Commit: 2e08308d62f381312b3da9dac8970dcdad4b3f2d Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-branches@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commits to the stable branches of the FreeBSD src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 06 Apr 2021 19:18:15 -0000 The branch stable/13 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=2e08308d62f381312b3da9dac8970dcdad4b3f2d commit 2e08308d62f381312b3da9dac8970dcdad4b3f2d Author: Mark Johnston AuthorDate: 2021-03-15 20:02:17 +0000 Commit: Mark Johnston CommitDate: 2021-04-06 18:50:46 +0000 vm_fault: Shoot down multiply mapped COW source page mappings Reviewed by: kib, rlibby Discussed with: alc Approved by: so Security: CVE-2021-29626 Security: FreeBSD-SA-21:08.vm (cherry picked from commit 982693bb729badac4e65ecd59772979f2849a2b2) --- sys/vm/vm_fault.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c index 585e1544415d..0e8ff9b27ed1 100644 --- a/sys/vm/vm_fault.c +++ b/sys/vm/vm_fault.c @@ -896,6 +896,9 @@ vm_fault_cow(struct faultstate *fs) { bool is_first_object_locked; + KASSERT(fs->object != fs->first_object, + ("source and target COW objects are identical")); + /* * This allows pages to be virtually copied from a backing_object * into the first_object, where the backing object has no other @@ -959,11 +962,29 @@ vm_fault_cow(struct faultstate *fs) */ fs->m_cow = fs->m; fs->m = NULL; + + /* + * Typically, the shadow object is either private to this + * address space (OBJ_ONEMAPPING) or its pages are read only. + * In the highly unusual case where the pages of a shadow object + * are read/write shared between this and other address spaces, + * we need to ensure that any pmap-level mappings to the + * original, copy-on-write page from the backing object are + * removed from those other address spaces. + * + * The flag check is racy, but this is tolerable: if + * OBJ_ONEMAPPING is cleared after the check, the busy state + * ensures that new mappings of m_cow can't be created. + * pmap_enter() will replace an existing mapping in the current + * address space. If OBJ_ONEMAPPING is set after the check, + * removing mappings will at worse trigger some unnecessary page + * faults. + */ + vm_page_assert_xbusied(fs->m_cow); + if ((fs->first_object->flags & OBJ_ONEMAPPING) == 0) + pmap_remove_all(fs->m_cow); } - /* - * fs->object != fs->first_object due to above - * conditional - */ + vm_object_pip_wakeup(fs->object); /*