From owner-dev-commits-src-branches@freebsd.org Fri Feb 19 21:49:53 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 DA399540D5B; Fri, 19 Feb 2021 21:49:53 +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 4Dj4xF5p0Fz3NMW; Fri, 19 Feb 2021 21:49:53 +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 BA0A11365A; Fri, 19 Feb 2021 21:49:53 +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 11JLnrqf040950; Fri, 19 Feb 2021 21:49:53 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 11JLnrxm040949; Fri, 19 Feb 2021 21:49:53 GMT (envelope-from git) Date: Fri, 19 Feb 2021 21:49:53 GMT Message-Id: <202102192149.11JLnrxm040949@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org From: Jamie Gritton Subject: git: c837631bd47a - stable/11 - MFC jail: Handle a possible race between jail_remove(2) and fork(2) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: jamie X-Git-Repository: src X-Git-Refname: refs/heads/stable/11 X-Git-Reftype: branch X-Git-Commit: c837631bd47af73d03e3d8907f1e58b88403007c 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: Fri, 19 Feb 2021 21:49:53 -0000 The branch stable/11 has been updated by jamie: URL: https://cgit.FreeBSD.org/src/commit/?id=c837631bd47af73d03e3d8907f1e58b88403007c commit c837631bd47af73d03e3d8907f1e58b88403007c Author: Jamie Gritton AuthorDate: 2021-02-16 19:19:13 +0000 Commit: Jamie Gritton CommitDate: 2021-02-19 21:49:34 +0000 MFC jail: Handle a possible race between jail_remove(2) and fork(2) jail_remove(2) includes a loop that sends SIGKILL to all processes in a jail, but skips processes in PRS_NEW state. Thus it is possible the a process in mid-fork(2) during jail removal can survive the jail being removed. Add a prison flag PR_REMOVE, which is checked before the new process returns. If the jail is being removed, the process will then exit. Also check this flag in jail_attach(2) which has a similar issue. Reported by: trasz Approved by: kib (cherry picked from commit cc7b73065302005ebc4a19503188c8d6d5eb923d) --- sys/kern/kern_fork.c | 6 ++++++ sys/kern/kern_jail.c | 18 ++++++++++++++++++ sys/sys/jail.h | 1 + 3 files changed, 25 insertions(+) diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c index 2aa5f405d3c2..ea35afb42f99 100644 --- a/sys/kern/kern_fork.c +++ b/sys/kern/kern_fork.c @@ -1144,6 +1144,12 @@ fork_return(struct thread *td, struct trapframe *frame) PROC_UNLOCK(p); } + /* + * If the prison was killed mid-fork, die along with it. + */ + if (td->td_ucred->cr_prison->pr_flags & PR_REMOVE) + exit1(td, 0, SIGKILL); + userret(td, frame); #ifdef KTRACE diff --git a/sys/kern/kern_jail.c b/sys/kern/kern_jail.c index 47cc3ddd3bce..0bb9c76a25c9 100644 --- a/sys/kern/kern_jail.c +++ b/sys/kern/kern_jail.c @@ -1751,6 +1751,7 @@ kern_jail_set(struct thread *td, struct uio *optuio, int flags) } } pr->pr_flags = (pr->pr_flags & ~ch_flags) | pr_flags; + pr->pr_flags &= ~PR_REMOVE; mtx_unlock(&pr->pr_mtx); #ifdef RACCT @@ -2287,6 +2288,12 @@ prison_remove_one(struct prison *pr) struct proc *p; int deuref; + /* + * Mark the prison as doomed, so it doesn't accidentally come back + * to life. It may still be explicitly brought back by jail_set(2). + */ + pr->pr_flags |= PR_REMOVE; + /* If the prison was persistent, it is not anymore. */ deuref = 0; if (pr->pr_flags & PR_PERSIST) { @@ -2431,6 +2438,17 @@ do_jail_attach(struct thread *td, struct prison *pr) #endif prison_deref(oldcred->cr_prison, PD_DEREF | PD_DEUREF); crfree(oldcred); + + /* + * If the prison was killed while changing credentials, die along + * with it. + */ + if (pr->pr_flags & PR_REMOVE) { + PROC_LOCK(p); + kern_psignal(p, SIGKILL); + PROC_UNLOCK(p); + } + return (0); e_unlock: diff --git a/sys/sys/jail.h b/sys/sys/jail.h index 7142d0d0d71a..90a3fbce821f 100644 --- a/sys/sys/jail.h +++ b/sys/sys/jail.h @@ -209,6 +209,7 @@ struct prison_racct { /* primary jail address. */ /* Internal flag bits */ +#define PR_REMOVE 0x01000000 /* In process of being removed */ #define PR_IP4 0x02000000 /* IPv4 restricted or disabled */ /* by this jail or an ancestor */ #define PR_IP6 0x04000000 /* IPv6 restricted or disabled */