Messages in this thread Patch in this message | | | Date | Wed, 18 Jun 2008 19:09:19 +0200 | From | Benjamin Thery <> | Subject | [PATCH 11/11] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched |
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Mark the /sys/kernel/uids directory to be tagged so that processes in different user namespaces can remount /sys and see their own uid listings.
Without this patch, having CONFIG_FAIR_SCHED=y makes user namespaces unusable, because when you clone(CLONE_NEWUSER) it will auto-create the root userid and try to create /sys/kernel/uids/0. Since that already exists from the parent user namespace, the create fails, and the clone misleadingly ends up returning -ENOMEM.
This patch fixes the issue by allowing each user namespace to remount /sys, and having /sys filter the /sys/kernel/uid/ entries by user namespace.
Signed-off-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: Benjamin Thery <benjamin.thery@bull.net> --- fs/sysfs/mount.c | 3 +++ include/linux/sched.h | 1 + include/linux/sysfs.h | 2 ++ kernel/user.c | 21 +++++++++++++++++++++ kernel/user_namespace.c | 13 ++++++++++++- 5 files changed, 39 insertions(+), 1 deletion(-)
Index: linux-mm/fs/sysfs/mount.c =================================================================== --- linux-mm.orig/fs/sysfs/mount.c +++ linux-mm/fs/sysfs/mount.c @@ -81,6 +81,7 @@ static int sysfs_fill_super(struct super sb->s_root = root; sb->s_fs_info = info; info->tag.net_ns = hold_net(current->nsproxy->net_ns); + info->tag.user_ns = current->nsproxy->user_ns; return 0; out_err: @@ -100,6 +101,8 @@ static int sysfs_test_super(struct super if (task->nsproxy->net_ns != info->tag.net_ns) found = 0; + if (task->nsproxy->user_ns != info->tag.user_ns) + found = 0; return found; } Index: linux-mm/include/linux/sched.h =================================================================== --- linux-mm.orig/include/linux/sched.h +++ linux-mm/include/linux/sched.h @@ -604,6 +604,7 @@ struct user_struct { /* Hash table maintenance information */ struct hlist_node uidhash_node; uid_t uid; + struct user_namespace *user_ns; #ifdef CONFIG_USER_SCHED struct task_group *tg; Index: linux-mm/include/linux/sysfs.h =================================================================== --- linux-mm.orig/include/linux/sysfs.h +++ linux-mm/include/linux/sysfs.h @@ -20,6 +20,7 @@ struct kobject; struct module; struct net; +struct user_namespace; extern int kobject_set_name(struct kobject *kobj, const char *name, ...) __attribute__((format(printf, 2, 3))); @@ -83,6 +84,7 @@ struct sysfs_ops { struct sysfs_tag_info { struct net *net_ns; + struct user_namespace *user_ns; }; struct sysfs_tagged_dir_operations { Index: linux-mm/kernel/user.c =================================================================== --- linux-mm.orig/kernel/user.c +++ linux-mm/kernel/user.c @@ -53,6 +53,7 @@ struct user_struct root_user = { .files = ATOMIC_INIT(0), .sigpending = ATOMIC_INIT(0), .locked_shm = 0, + .user_ns = &init_user_ns, #ifdef CONFIG_USER_SCHED .tg = &init_task_group, #endif @@ -236,6 +237,23 @@ static void uids_release(struct kobject return; } +static const void *userns_sb_tag(struct sysfs_tag_info *info) +{ + return info->user_ns; +} + +static const void *userns_kobject_tag(struct kobject *kobj) +{ + struct user_struct *up; + up = container_of(kobj, struct user_struct, kobj); + return up->user_ns; +} + +static struct sysfs_tagged_dir_operations userns_tagged_dir_operations = { + .sb_tag = userns_sb_tag, + .kobject_tag = userns_kobject_tag, +}; + static struct kobj_type uids_ktype = { .sysfs_ops = &kobj_sysfs_ops, .default_attrs = uids_attributes, @@ -272,6 +290,8 @@ int __init uids_sysfs_init(void) if (!uids_kset) return -ENOMEM; + sysfs_enable_tagging(&uids_kset->kobj, &userns_tagged_dir_operations); + return uids_user_create(&root_user); } @@ -404,6 +424,7 @@ struct user_struct *alloc_uid(struct use goto out_unlock; new->uid = uid; + new->user_ns = ns; atomic_set(&new->__count, 1); if (sched_create_user(new) < 0) Index: linux-mm/kernel/user_namespace.c =================================================================== --- linux-mm.orig/kernel/user_namespace.c +++ linux-mm/kernel/user_namespace.c @@ -22,7 +22,7 @@ static struct user_namespace *clone_user struct user_struct *new_user; int n; - ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL); + ns = kzalloc(sizeof(struct user_namespace), GFP_KERNEL); if (!ns) return ERR_PTR(-ENOMEM); @@ -66,11 +66,22 @@ struct user_namespace * copy_user_ns(int return new_ns; } +/* clear sysfs tag when user namespace exits */ +static void sysfs_userns_exit(struct sysfs_tag_info *tag_info, void *data) +{ + struct user_namespace *ns = (struct user_namespace *)data; + + if (tag_info->user_ns != ns) + return; + tag_info->user_ns = NULL; +} + void free_user_ns(struct kref *kref) { struct user_namespace *ns; ns = container_of(kref, struct user_namespace, kref); + sysfs_ns_exit(sysfs_userns_exit, ns); release_uids(ns); kfree(ns); } --
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