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. Changelong: v2 - Reworked for the updated sysfs api Signed-off-by: Serge Hallyn <serue@xxxxxxxxxx> Signed-off-by: Benjamin Thery <benjamin.thery@xxxxxxxx> Signed-off-by: Daniel Lezcano <dlezcano@xxxxxxxxxx> Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> --- include/linux/sched.h | 1 + include/linux/sysfs.h | 1 + kernel/user.c | 22 ++++++++++++++++++++++ kernel/user_namespace.c | 1 + 4 files changed, 25 insertions(+), 0 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index c5d3f84..d2be6a5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -598,6 +598,7 @@ 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; diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h index 1ed31bb..ecb942c 100644 --- a/include/linux/sysfs.h +++ b/include/linux/sysfs.h @@ -81,6 +81,7 @@ struct sysfs_ops { enum sysfs_tag_type { SYSFS_TAG_TYPE_NONE = 0, SYSFS_TAG_TYPE_NETNS, + SYSFS_TAG_TYPE_USERNS, SYSFS_TAG_TYPES }; diff --git a/kernel/user.c b/kernel/user.c index 865ecf5..ca29fbc 100644 --- a/kernel/user.c +++ b/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 @@ -230,16 +231,33 @@ static struct attribute *uids_attributes[] = { NULL }; +static const void *uids_mount_tag(void) +{ + return current->nsproxy->user_ns; +} + +static struct sysfs_tag_type_operations uids_tag_type_operations = { + .mount_tag = uids_mount_tag, +}; + /* the lifetime of user_struct is not managed by the core (now) */ static void uids_release(struct kobject *kobj) { return; } +static const void *uids_sysfs_tag(struct kobject *kobj) +{ + struct user_struct *up; + up = container_of(kobj, struct user_struct, kobj); + return up->user_ns; +} + static struct kobj_type uids_ktype = { .sysfs_ops = &kobj_sysfs_ops, .default_attrs = uids_attributes, .release = uids_release, + .sysfs_tag = uids_sysfs_tag, }; /* create /sys/kernel/uids/<uid>/cpu_share file for this user */ @@ -272,6 +290,9 @@ int __init uids_sysfs_init(void) if (!uids_kset) return -ENOMEM; + sysfs_register_tag_type(SYSFS_TAG_TYPE_USERNS, &uids_tag_type_operations); + sysfs_make_tagged_dir(&uids_kset->kobj, SYSFS_TAG_TYPE_USERNS); + return uids_user_create(&root_user); } @@ -405,6 +426,7 @@ struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid) new->uid = uid; atomic_set(&new->__count, 1); + new->user_ns = ns; if (sched_create_user(new) < 0) goto out_free_user; diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index a9ab059..f67bbe0 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -71,6 +71,7 @@ void free_user_ns(struct kref *kref) struct user_namespace *ns; ns = container_of(kref, struct user_namespace, kref); + sysfs_exit_tag(SYSFS_TAG_TYPE_USERNS, ns); release_uids(ns); kfree(ns); } -- 1.5.3.rc6.17.g1911 _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers