Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755554AbYGKP57 (ORCPT ); Fri, 11 Jul 2008 11:57:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752750AbYGKP5w (ORCPT ); Fri, 11 Jul 2008 11:57:52 -0400 Received: from sacred.ru ([62.205.161.221]:38032 "EHLO sacred.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752671AbYGKP5v (ORCPT ); Fri, 11 Jul 2008 11:57:51 -0400 Message-ID: <48777BC8.7040507@openvz.org> Date: Fri, 11 Jul 2008 19:27:04 +0400 From: Pavel Emelyanov User-Agent: Thunderbird 2.0.0.14 (X11/20080421) MIME-Version: 1.0 To: Andrew Morton CC: Serge Hallyn , Linux Kernel Mailing List Subject: [PATCH] devcgroup: relax white-list protection down to RCU Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-3.0 (sacred.ru [62.205.161.221]); Fri, 11 Jul 2008 19:29:27 +0400 (MSD) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3995 Lines: 132 Currently this list is protected with a simple spinlock, even for reading from one. This is OK, but can be better. Actually I want it to be better very much, since after replacing the OpenVZ device permissions engine with the cgroup-based one I noticed, that we set 12 default device permissions for each newly created container (for /dev/null, full, terminals, ect devices), and people sometimes have up to 20 perms more, so traversing the ~30-40 elements list under a spinlock doesn't seem very good. Here's the RCU protection for white-list - dev_whitelist_item-s are added and removed under the devcg->lock, but are looked up in permissions checking under the rcu_read_lock. Signed-off-by: Pavel Emelyanov Acked-by: Serge Hallyn --- diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 0bbd705..5d447a4 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -41,6 +41,7 @@ struct dev_whitelist_item { short type; short access; struct list_head list; + struct rcu_head rcu; }; struct dev_cgroup { @@ -133,11 +134,19 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, } if (whcopy != NULL) - list_add_tail(&whcopy->list, &dev_cgroup->whitelist); + list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist); spin_unlock(&dev_cgroup->lock); return 0; } +static void whitelist_item_free(struct rcu_head *rcu) +{ + struct dev_whitelist_item *item; + + item = container_of(rcu, struct dev_whitelist_item, rcu); + kfree(item); +} + /* * called under cgroup_lock() * since the list is visible to other tasks, we need the spinlock also @@ -161,8 +170,8 @@ static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup, remove: walk->access &= ~wh->access; if (!walk->access) { - list_del(&walk->list); - kfree(walk); + list_del_rcu(&walk->list); + call_rcu(&walk->rcu, whitelist_item_free); } } spin_unlock(&dev_cgroup->lock); @@ -269,15 +278,15 @@ static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, struct dev_whitelist_item *wh; char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; - spin_lock(&devcgroup->lock); - list_for_each_entry(wh, &devcgroup->whitelist, list) { + rcu_read_lock(); + list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) { set_access(acc, wh->access); set_majmin(maj, wh->major); set_majmin(min, wh->minor); seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type), maj, min, acc); } - spin_unlock(&devcgroup->lock); + rcu_read_unlock(); return 0; } @@ -508,8 +517,8 @@ int devcgroup_inode_permission(struct inode *inode, int mask) if (!dev_cgroup) return 0; - spin_lock(&dev_cgroup->lock); - list_for_each_entry(wh, &dev_cgroup->whitelist, list) { + rcu_read_lock(); + list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { if (wh->type & DEV_ALL) goto acc_check; if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode)) @@ -525,10 +534,10 @@ acc_check: continue; if ((mask & MAY_READ) && !(wh->access & ACC_READ)) continue; - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return 0; } - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return -EPERM; } @@ -543,7 +552,7 @@ int devcgroup_inode_mknod(int mode, dev_t dev) if (!dev_cgroup) return 0; - spin_lock(&dev_cgroup->lock); + rcu_read_lock(); list_for_each_entry(wh, &dev_cgroup->whitelist, list) { if (wh->type & DEV_ALL) goto acc_check; @@ -558,9 +567,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev) acc_check: if (!(wh->access & ACC_MKNOD)) continue; - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return 0; } - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return -EPERM; } -- 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/