From owner-svn-src-head@FreeBSD.ORG Tue May 20 15:35:12 2014 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 846D828D; Tue, 20 May 2014 15:35:12 +0000 (UTC) Received: from vps1.elischer.org (vps1.elischer.org [204.109.63.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "vps1.elischer.org", Issuer "CA Cert Signing Authority" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 61A3121D5; Tue, 20 May 2014 15:35:11 +0000 (UTC) Received: from Julian-MBP3.local (ppp121-45-232-70.lns20.per1.internode.on.net [121.45.232.70]) (authenticated bits=0) by vps1.elischer.org (8.14.8/8.14.8) with ESMTP id s4KFZ6Wf063809 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Tue, 20 May 2014 08:35:09 -0700 (PDT) (envelope-from julian@freebsd.org) Message-ID: <537B7625.4080908@freebsd.org> Date: Tue, 20 May 2014 23:35:01 +0800 From: Julian Elischer User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Konstantin Belousov , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r266464 - in head/sys: kern sys vm References: <201405200919.s4K9JZvg087765@svn.freebsd.org> In-Reply-To: <201405200919.s4K9JZvg087765@svn.freebsd.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 May 2014 15:35:12 -0000 On 5/20/14, 5:19 PM, Konstantin Belousov wrote: > Author: kib > Date: Tue May 20 09:19:35 2014 > New Revision: 266464 > URL: http://svnweb.freebsd.org/changeset/base/266464 > > Log: > When exec_new_vmspace() decides that current vmspace cannot be reused > on execve(2), it calls vmspace_exec(), which frees the current > vmspace. The thread executing an exec syscall gets new vmspace > assigned, and old vmspace is freed if only referenced by the current > process. The free operation includes pmap_release(), which > de-constructs the paging structures used by hardware. > > If the calling process is multithreaded, other threads are suspended > in the thread_suspend_check(), and need to be unsuspended and run to > be able to exit on successfull exec. Now, since the old vmspace is > destroyed, paging structures are invalid, threads are resumed on the > non-existent pmaps (page tables), which leads to triple fault on x86. > > To fix, postpone the free of old vmspace until the threads are resumed > and exited. To avoid modifications to all image activators all of > which use exec_new_vmspace(), memoize the current (old) vmspace in > kern_execve(), and notify it about the need to call vmspace_free() > with a thread-private flag TDP_EXECVMSPC. I was sure that we covered this case at some time in the past.. I think all threads but the caller were killed at the kernel boundary and exec waited for that to happen. > > http://bugs.debian.org/743141 > > Reported by: Ivo De Decker through secteam > Sponsored by: The FreeBSD Foundation > MFC after: 3 days > > Modified: > head/sys/kern/kern_exec.c > head/sys/sys/proc.h > head/sys/vm/vm_map.c > > Modified: head/sys/kern/kern_exec.c > ============================================================================== > --- head/sys/kern/kern_exec.c Tue May 20 03:00:20 2014 (r266463) > +++ head/sys/kern/kern_exec.c Tue May 20 09:19:35 2014 (r266464) > @@ -282,6 +282,7 @@ kern_execve(td, args, mac_p) > struct mac *mac_p; > { > struct proc *p = td->td_proc; > + struct vmspace *oldvmspace; > int error; > > AUDIT_ARG_ARGV(args->begin_argv, args->argc, > @@ -298,6 +299,8 @@ kern_execve(td, args, mac_p) > PROC_UNLOCK(p); > } > > + KASSERT((td->td_pflags & TDP_EXECVMSPC) == 0, ("nested execve")); > + oldvmspace = td->td_proc->p_vmspace; > error = do_execve(td, args, mac_p); > > if (p->p_flag & P_HADTHREADS) { > @@ -312,6 +315,12 @@ kern_execve(td, args, mac_p) > thread_single_end(); > PROC_UNLOCK(p); > } > + if ((td->td_pflags & TDP_EXECVMSPC) != 0) { > + KASSERT(td->td_proc->p_vmspace != oldvmspace, > + ("oldvmspace still used")); > + vmspace_free(oldvmspace); > + td->td_pflags &= ~TDP_EXECVMSPC; > + } > > return (error); > } > > Modified: head/sys/sys/proc.h > ============================================================================== > --- head/sys/sys/proc.h Tue May 20 03:00:20 2014 (r266463) > +++ head/sys/sys/proc.h Tue May 20 09:19:35 2014 (r266464) > @@ -429,6 +429,7 @@ do { \ > #define TDP_NERRNO 0x08000000 /* Last errno is already in td_errno */ > #define TDP_UIOHELD 0x10000000 /* Current uio has pages held in td_ma */ > #define TDP_DEVMEMIO 0x20000000 /* Accessing memory for /dev/mem */ > +#define TDP_EXECVMSPC 0x40000000 /* Execve destroyed old vmspace */ > > /* > * Reasons that the current thread can not be run yet. > > Modified: head/sys/vm/vm_map.c > ============================================================================== > --- head/sys/vm/vm_map.c Tue May 20 03:00:20 2014 (r266463) > +++ head/sys/vm/vm_map.c Tue May 20 09:19:35 2014 (r266464) > @@ -3758,6 +3758,8 @@ vmspace_exec(struct proc *p, vm_offset_t > struct vmspace *oldvmspace = p->p_vmspace; > struct vmspace *newvmspace; > > + KASSERT((curthread->td_pflags & TDP_EXECVMSPC) == 0, > + ("vmspace_exec recursed")); > newvmspace = vmspace_alloc(minuser, maxuser, NULL); > if (newvmspace == NULL) > return (ENOMEM); > @@ -3774,7 +3776,7 @@ vmspace_exec(struct proc *p, vm_offset_t > PROC_VMSPACE_UNLOCK(p); > if (p == curthread->td_proc) > pmap_activate(curthread); > - vmspace_free(oldvmspace); > + curthread->td_pflags |= TDP_EXECVMSPC; > return (0); > } > > > >