Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030747AbXAZF1I (ORCPT ); Fri, 26 Jan 2007 00:27:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030751AbXAZF1H (ORCPT ); Fri, 26 Jan 2007 00:27:07 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:34641 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030747AbXAZF1G (ORCPT ); Fri, 26 Jan 2007 00:27:06 -0500 Date: Thu, 25 Jan 2007 23:26:59 -0600 From: "Serge E. Hallyn" To: linux-kernel@vger.kernel.org Cc: "Eric W. Biederman" , Oleg Nesterov , Cedric Le Goater , Daniel Hokka Zakrisson , herbert@13thfloor.at, akpm@osdl.org, trond.myklebust@fys.uio.no, Linux Containers Subject: [PATCH] namespaces: fix exit race by splitting exit Message-ID: <20070126052659.GA23250@sergelap.austin.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4648 Lines: 174 Ok, could you verify that the following patch at least solves the oopsing? (I can't reproduce the oops with Daniel's test prog) thanks, -serge From: Serge E. Hallyn Subject: [PATCH] namespaces: fix exit race by splitting exit Fix exit race by splitting the nsproxy putting into two pieces. First piece reduces the nsproxy refcount. If we dropped the last reference, then it puts the mnt_ns, and returns the nsproxy as a hint to the caller. Else it returns NULL. The second piece of exiting task namespaces sets tsk->nsproxy to NULL, and drops the references to other namespaces and frees the nsproxy only if an nsproxy was passed in. A little awkward and should probably be reworked, but hopefully it fixes the NFS oops. Signed-off-by: Serge E. Hallyn --- include/linux/nsproxy.h | 30 +++++++++++++++++++----------- kernel/exit.c | 6 ++++-- kernel/fork.c | 4 ++-- kernel/nsproxy.c | 16 +++++++++++++++- 4 files changed, 40 insertions(+), 16 deletions(-) ab969afa3624aba0bc26dc237d27178137c05d46 diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h index 0b9f0dc..678e1d3 100644 --- a/include/linux/nsproxy.h +++ b/include/linux/nsproxy.h @@ -35,22 +35,30 @@ struct nsproxy *dup_namespaces(struct ns int copy_namespaces(int flags, struct task_struct *tsk); void get_task_namespaces(struct task_struct *tsk); void free_nsproxy(struct nsproxy *ns); +struct nsproxy *put_nsproxy(struct nsproxy *ns); -static inline void put_nsproxy(struct nsproxy *ns) +static inline void finalize_put_nsproxy(struct nsproxy *ns) { - if (atomic_dec_and_test(&ns->count)) { + if (ns) free_nsproxy(ns); - } } -static inline void exit_task_namespaces(struct task_struct *p) +static inline void put_and_finalize_nsproxy(struct nsproxy *ns) { - struct nsproxy *ns = p->nsproxy; - if (ns) { - task_lock(p); - p->nsproxy = NULL; - task_unlock(p); - put_nsproxy(ns); - } + finalize_put_nsproxy(put_nsproxy(ns)); +} + +static inline struct nsproxy *preexit_task_namespaces(struct task_struct *p) +{ + return put_nsproxy(p->nsproxy); +} + +static inline void exit_task_namespaces(struct task_struct *p, + struct nsproxy *ns) +{ + task_lock(p); + p->nsproxy = NULL; + task_unlock(p); + finalize_put_nsproxy(ns); } #endif diff --git a/kernel/exit.c b/kernel/exit.c index 3540172..a5bf532 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -396,7 +396,7 @@ void daemonize(const char *name, ...) current->fs = fs; atomic_inc(&fs->count); - exit_task_namespaces(current); + put_and_finalize_nsproxy(current->nsproxy); current->nsproxy = init_task.nsproxy; get_task_namespaces(current); @@ -853,6 +853,7 @@ static void exit_notify(struct task_stru fastcall NORET_TYPE void do_exit(long code) { struct task_struct *tsk = current; + struct nsproxy *ns; int group_dead; profile_task_exit(tsk); @@ -938,8 +939,9 @@ fastcall NORET_TYPE void do_exit(long co tsk->exit_code = code; proc_exit_connector(tsk); + ns = preexit_task_namespaces(tsk); exit_notify(tsk); - exit_task_namespaces(tsk); + exit_task_namespaces(tsk, ns); #ifdef CONFIG_NUMA mpol_free(tsk->mempolicy); tsk->mempolicy = NULL; diff --git a/kernel/fork.c b/kernel/fork.c index fc723e5..4cf8684 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1265,7 +1265,7 @@ static struct task_struct *copy_process( return p; bad_fork_cleanup_namespaces: - exit_task_namespaces(p); + put_and_finalize_nsproxy(p->nsproxy); bad_fork_cleanup_keys: exit_keys(p); bad_fork_cleanup_mm: @@ -1711,7 +1711,7 @@ asmlinkage long sys_unshare(unsigned lon } if (new_nsproxy) - put_nsproxy(new_nsproxy); + put_and_finalize_nsproxy(new_nsproxy); bad_unshare_cleanup_ipc: if (new_ipc) diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c index f5b9ee6..7b05bce 100644 --- a/kernel/nsproxy.c +++ b/kernel/nsproxy.c @@ -117,7 +117,7 @@ int copy_namespaces(int flags, struct ta goto out_pid; out: - put_nsproxy(old_ns); + put_and_finalize_nsproxy(old_ns); return err; out_pid: @@ -135,6 +135,20 @@ out_ns: goto out; } +struct nsproxy *put_nsproxy(struct nsproxy *ns) +{ + if (ns) { + if (atomic_dec_and_test(&ns->count)) { + if (ns->mnt_ns) { + put_mnt_ns(ns->mnt_ns); + ns->mnt_ns = NULL; + } + return ns; + } + } + return NULL; +} + void free_nsproxy(struct nsproxy *ns) { if (ns->mnt_ns) -- 1.1.6 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/