From owner-svn-src-all@freebsd.org Wed Nov 6 16:59:17 2019 Return-Path: Delivered-To: svn-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 9F1B31BA744; Wed, 6 Nov 2019 16:59:17 +0000 (UTC) (envelope-from markj@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) server-signature RSA-PSS (4096 bits) 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 477XnK3VwKz4Lgn; Wed, 6 Nov 2019 16:59:17 +0000 (UTC) (envelope-from markj@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 42AEF137; Wed, 6 Nov 2019 16:59:17 +0000 (UTC) (envelope-from markj@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id xA6GxHHq048101; Wed, 6 Nov 2019 16:59:17 GMT (envelope-from markj@FreeBSD.org) Received: (from markj@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id xA6GxGwe048100; Wed, 6 Nov 2019 16:59:16 GMT (envelope-from markj@FreeBSD.org) Message-Id: <201911061659.xA6GxGwe048100@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: markj set sender to markj@FreeBSD.org using -f From: Mark Johnston Date: Wed, 6 Nov 2019 16:59:16 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r354400 - head/sys/vm X-SVN-Group: head X-SVN-Commit-Author: markj X-SVN-Commit-Paths: head/sys/vm X-SVN-Commit-Revision: 354400 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Nov 2019 16:59:17 -0000 Author: markj Date: Wed Nov 6 16:59:16 2019 New Revision: 354400 URL: https://svnweb.freebsd.org/changeset/base/354400 Log: Fix a race in release_page(). Since r354156 we may call release_page() without the page's object lock held, specifically following the page copy during a CoW fault. release_page() must therefore unbusy the page only after scheduling the requeue, to avoid racing with a free of the page. Previously, the object lock prevented this race from occurring. Add some assertions that were helpful in tracking this down. Reported by: pho, syzkaller Tested by: pho Reviewed by: alc, jeff, kib Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D22234 Modified: head/sys/vm/vm_fault.c head/sys/vm/vm_page.c Modified: head/sys/vm/vm_fault.c ============================================================================== --- head/sys/vm/vm_fault.c Wed Nov 6 16:21:35 2019 (r354399) +++ head/sys/vm/vm_fault.c Wed Nov 6 16:59:16 2019 (r354400) @@ -155,10 +155,14 @@ release_page(struct faultstate *fs) { if (fs->m != NULL) { - vm_page_xunbusy(fs->m); + /* + * fs->m's object lock might not be held, so the page must be + * kept busy until we are done with it. + */ vm_page_lock(fs->m); vm_page_deactivate(fs->m); vm_page_unlock(fs->m); + vm_page_xunbusy(fs->m); fs->m = NULL; } } Modified: head/sys/vm/vm_page.c ============================================================================== --- head/sys/vm/vm_page.c Wed Nov 6 16:21:35 2019 (r354399) +++ head/sys/vm/vm_page.c Wed Nov 6 16:59:16 2019 (r354400) @@ -3421,7 +3421,7 @@ vm_page_dequeue(vm_page_t m) struct vm_pagequeue *pq, *pq1; uint8_t aflags; - KASSERT(mtx_owned(vm_page_lockptr(m)) || m->object == NULL, + KASSERT(mtx_owned(vm_page_lockptr(m)) || m->ref_count == 0, ("page %p is allocated and unlocked", m)); for (pq = vm_page_pagequeue(m);; pq = pq1) { @@ -3475,6 +3475,8 @@ vm_page_enqueue(vm_page_t m, uint8_t queue) vm_page_assert_locked(m); KASSERT(m->queue == PQ_NONE && (m->aflags & PGA_QUEUE_STATE_MASK) == 0, ("%s: page %p is already enqueued", __func__, m)); + KASSERT(m->ref_count > 0, + ("%s: page %p does not carry any references", __func__, m)); m->queue = queue; if ((m->aflags & PGA_REQUEUE) == 0) @@ -3496,6 +3498,8 @@ vm_page_requeue(vm_page_t m) vm_page_assert_locked(m); KASSERT(vm_page_queue(m) != PQ_NONE, ("%s: page %p is not logically enqueued", __func__, m)); + KASSERT(m->ref_count > 0, + ("%s: page %p does not carry any references", __func__, m)); if ((m->aflags & PGA_REQUEUE) == 0) vm_page_aflag_set(m, PGA_REQUEUE); @@ -3889,6 +3893,8 @@ vm_page_mvqueue(vm_page_t m, const uint8_t nqueue) vm_page_assert_locked(m); KASSERT((m->oflags & VPO_UNMANAGED) == 0, ("vm_page_mvqueue: page %p is unmanaged", m)); + KASSERT(m->ref_count > 0, + ("%s: page %p does not carry any references", __func__, m)); if (vm_page_queue(m) != nqueue) { vm_page_dequeue(m);