From owner-svn-src-all@freebsd.org Mon Apr 13 19:20:39 2020 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 B693D2C6C8A; Mon, 13 Apr 2020 19:20:39 +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 491JP34RxWz44QD; Mon, 13 Apr 2020 19:20:39 +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 9400020601; Mon, 13 Apr 2020 19:20:39 +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 03DJKdoF001419; Mon, 13 Apr 2020 19:20:39 GMT (envelope-from markj@FreeBSD.org) Received: (from markj@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 03DJKdTU001418; Mon, 13 Apr 2020 19:20:39 GMT (envelope-from markj@FreeBSD.org) Message-Id: <202004131920.03DJKdTU001418@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: markj set sender to markj@FreeBSD.org using -f From: Mark Johnston Date: Mon, 13 Apr 2020 19:20:39 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r359892 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: markj X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 359892 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: Mon, 13 Apr 2020 19:20:39 -0000 Author: markj Date: Mon Apr 13 19:20:39 2020 New Revision: 359892 URL: https://svnweb.freebsd.org/changeset/base/359892 Log: Relax restrictions on private mappings of POSIX shm objects. When creating a private mapping of a POSIX shared memory object, VM_PROT_WRITE should always be included in maxprot regardless of permissions on the underlying FD. Otherwise it is possible to open a shm object read-only, map it with MAP_PRIVATE and PROT_WRITE, and violate the invariant in vm_map_insert() that (prot & maxprot) == prot. Reported by: syzkaller Reviewed by: kevans, kib MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D24398 Modified: head/sys/kern/uipc_shm.c Modified: head/sys/kern/uipc_shm.c ============================================================================== --- head/sys/kern/uipc_shm.c Mon Apr 13 17:55:31 2020 (r359891) +++ head/sys/kern/uipc_shm.c Mon Apr 13 19:20:39 2020 (r359892) @@ -1136,23 +1136,28 @@ shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *a /* * If FWRITE's set, we can allow VM_PROT_WRITE unless it's a shared - * mapping with a write seal applied. + * mapping with a write seal applied. Private mappings are always + * writeable. */ - if ((fp->f_flag & FWRITE) != 0 && ((flags & MAP_SHARED) == 0 || - (shmfd->shm_seals & F_SEAL_WRITE) == 0)) + if ((flags & MAP_SHARED) == 0) { + cap_maxprot |= VM_PROT_WRITE; maxprot |= VM_PROT_WRITE; + writecnt = false; + } else { + if ((fp->f_flag & FWRITE) != 0 && + (shmfd->shm_seals & F_SEAL_WRITE) == 0) + maxprot |= VM_PROT_WRITE; + writecnt = (prot & VM_PROT_WRITE) != 0; + if (writecnt && (shmfd->shm_seals & F_SEAL_WRITE) != 0) { + error = EPERM; + goto out; + } - writecnt = (flags & MAP_SHARED) != 0 && (prot & VM_PROT_WRITE) != 0; - - if (writecnt && (shmfd->shm_seals & F_SEAL_WRITE) != 0) { - error = EPERM; - goto out; - } - - /* Don't permit shared writable mappings on read-only descriptors. */ - if (writecnt && (maxprot & VM_PROT_WRITE) == 0) { - error = EACCES; - goto out; + /* Don't permit shared writable mappings on read-only descriptors. */ + if (writecnt && (maxprot & VM_PROT_WRITE) == 0) { + error = EACCES; + goto out; + } } maxprot &= cap_maxprot;