From owner-dev-commits-src-all@freebsd.org Tue Jun 1 14:39:29 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 D12AE6556B0; Tue, 1 Jun 2021 14:39:29 +0000 (UTC) (envelope-from dchagin@heemeyer.club) Received: from heemeyer.club (heemeyer.club [IPv6:2001:19f0:6400:80a1:5054:ff:fe7a:a27d]) (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 mx1.freebsd.org (Postfix) with ESMTPS id 4FvZYY4txyz3Lls; Tue, 1 Jun 2021 14:39:29 +0000 (UTC) (envelope-from dchagin@heemeyer.club) Received: from heemeyer.club (localhost [127.0.0.1]) by heemeyer.club (8.16.1/8.16.1) with ESMTP id 151EdS5H002100; Tue, 1 Jun 2021 14:39:28 GMT (envelope-from dchagin@heemeyer.club) Received: (from dchagin@localhost) by heemeyer.club (8.16.1/8.16.1/Submit) id 151EdSN9002099; Tue, 1 Jun 2021 14:39:28 GMT (envelope-from dchagin) Date: Tue, 1 Jun 2021 14:39:28 +0000 From: Dmitry Chagin To: Mark Johnston Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: f3851b235b23 - main - ktrace: Fix a race with fork() Message-ID: References: <202105271953.14RJrN36017670@gitrepo.freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 4FvZYY4txyz3Lls X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] 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, 01 Jun 2021 14:39:29 -0000 On Tue, Jun 01, 2021 at 09:20:04AM -0400, Mark Johnston wrote: > On Tue, Jun 01, 2021 at 12:44:30PM +0000, Dmitry Chagin wrote: > > On Thu, May 27, 2021 at 07:53:23PM +0000, Mark Johnston wrote: > > > The branch main has been updated by markj: > > > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=f3851b235b23d9220ace31bbc89b1fe0a78fc75c > > > > > > commit f3851b235b23d9220ace31bbc89b1fe0a78fc75c > > > Author: Mark Johnston > > > AuthorDate: 2021-05-27 19:49:59 +0000 > > > Commit: Mark Johnston > > > CommitDate: 2021-05-27 19:52:20 +0000 > > > > > > ktrace: Fix a race with fork() > > > > > > ktrace(2) may toggle trace points in any of > > > 1. a single process > > > 2. all members of a process group > > > 3. all descendents of the processes in 1 or 2 > > > > > > In the first two cases, we do not permit the operation if the process is > > > being forked or not visible. However, in case 3 we did not enforce this > > > restriction for descendents. As a result, the assertions about the child > > > in ktrprocfork() may be violated. > > > > > > Move these checks into ktrops() so that they are applied consistently. > > > > > > Allow KTROP_CLEAR for nascent processes. Otherwise, there is a window > > > where we cannot clear trace points for a nascent child if they are > > > inherited from the parent. > > > > > > Reported by: syzbot+d96676592978f137e05c@syzkaller.appspotmail.com > > > Reported by: syzbot+7c98fcf84a4439f2817f@syzkaller.appspotmail.com > > > Reviewed by: kib > > > MFC after: 1 week > > > Sponsored by: The FreeBSD Foundation > > > Differential Revision: https://reviews.freebsd.org/D30481 > > > --- > > > sys/kern/kern_ktrace.c | 43 ++++++++++++++++++++++--------------------- > > > 1 file changed, 22 insertions(+), 21 deletions(-) > > > > > > diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c > > > index dc064d9ebd67..4a2dad20b035 100644 > > > --- a/sys/kern/kern_ktrace.c > > > +++ b/sys/kern/kern_ktrace.c > > > @@ -1006,7 +1006,7 @@ sys_ktrace(struct thread *td, struct ktrace_args *uap) > > > int facs = uap->facs & ~KTRFAC_ROOT; > > > int ops = KTROP(uap->ops); > > > int descend = uap->ops & KTRFLAG_DESCEND; > > > - int nfound, ret = 0; > > > + int ret = 0; > > > int flags, error = 0; > > > struct nameidata nd; > > > struct ktr_io_params *kiop, *old_kiop; > > > @@ -1080,42 +1080,31 @@ restart: > > > error = ESRCH; > > > goto done; > > > } > > > + > > > /* > > > * ktrops() may call vrele(). Lock pg_members > > > * by the proctree_lock rather than pg_mtx. > > > */ > > > PGRP_UNLOCK(pg); > > > - nfound = 0; > > > + if (LIST_EMPTY(&pg->pg_members)) { > > > + sx_sunlock(&proctree_lock); > > > + error = ESRCH; > > > + goto done; > > > + } > > > LIST_FOREACH(p, &pg->pg_members, p_pglist) { > > > PROC_LOCK(p); > > > - if (p->p_state == PRS_NEW || > > > - p_cansee(td, p) != 0) { > > > - PROC_UNLOCK(p); > > > - continue; > > > - } > > > - nfound++; > > > if (descend) > > > ret |= ktrsetchildren(td, p, ops, facs, kiop); > > > else > > > ret |= ktrops(td, p, ops, facs, kiop); > > > } > > > - if (nfound == 0) { > > > - sx_sunlock(&proctree_lock); > > > - error = ESRCH; > > > - goto done; > > > - } > > > } else { > > > /* > > > * by pid > > > */ > > > p = pfind(uap->pid); > > > - if (p == NULL) > > > + if (p == NULL) { > > > error = ESRCH; > > > - else > > > - error = p_cansee(td, p); > > > - if (error) { > > > - if (p != NULL) > > > - PROC_UNLOCK(p); > > > sx_sunlock(&proctree_lock); > > > goto done; > > > } > > > @@ -1187,8 +1176,20 @@ ktrops(struct thread *td, struct proc *p, int ops, int facs, > > > PROC_UNLOCK(p); > > > return (0); > > > } > > > - if (p->p_flag & P_WEXIT) { > > > - /* If the process is exiting, just ignore it. */ > > > + if ((ops == KTROP_SET && p->p_state == PRS_NEW) || !p_cansee(td, p)) { > > > > ^^^^^^^^^^^^^^ seems that it broke ktrace: > > root@mordor:~ # ktrace ls > > ktrace: ktrace.out: Operation not permitted > > Indeed, I pushed a fix to main. Sorry for the breakage. works now, thank you!