Create /proc/userns, which prints out all user namespaces. It
prints the address of the user_ns itself, the uid and userns address
of the user who created it, and the reference count.
Signed-off-by: Serge E. Hallyn <se...@us.ibm.com>
---
include/linux/user_namespace.h | 2 +
kernel/user.c | 1 +
kernel/user_namespace.c | 84 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 87 insertions(+), 0 deletions(-)
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index a2b82d5..e64d602 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -14,8 +14,10 @@ struct user_namespace {
struct hlist_head uidhash_table[UIDHASH_SZ];
struct user_struct *creator;
struct work_struct destroyer;
+ struct list_head list;
};
+extern spinlock_t usernslist_lock;
extern struct user_namespace init_user_ns;
#ifdef CONFIG_USER_NS
diff --git a/kernel/user.c b/kernel/user.c
index 850e0ba..6474422 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -23,6 +23,7 @@ struct user_namespace init_user_ns = {
.refcount = ATOMIC_INIT(2),
},
.creator = &root_user,
+ .list = LIST_HEAD_INIT(init_user_ns.list),
};
EXPORT_SYMBOL_GPL(init_user_ns);
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index e624b0f..8d7c725 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -10,6 +10,11 @@
#include <linux/slab.h>
#include <linux/user_namespace.h>
#include <linux/cred.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/spinlock.h>
+
+DEFINE_SPINLOCK(usernslist_lock);
static struct user_namespace *_new_user_ns(struct user_struct *creator,
struct user_struct **newroot)
@@ -40,6 +45,9 @@ static struct user_namespace *_new_user_ns(struct user_struct
*creator,
/* alloc_uid() incremented the userns refcount. Just set it to 1 */
kref_set(&ns->kref, 1);
+ spin_lock(&usernslist_lock);
+ list_add_tail(&ns->list, &init_user_ns.list);
+ spin_unlock(&usernslist_lock);
*newroot = root_user;
return ns;
}
@@ -90,6 +98,9 @@ static void free_user_ns_work(struct work_struct *work)
{
struct user_namespace *ns =
container_of(work, struct user_namespace, destroyer);
+ spin_lock(&usernslist_lock);
+ list_del(&ns->list);
+ spin_unlock(&usernslist_lock);
free_uid(ns->creator);
kfree(ns);
}
@@ -103,3 +114,76 @@ void free_user_ns(struct kref *kref)
schedule_work(&ns->destroyer);
}
EXPORT_SYMBOL(free_user_ns);
+
+#ifdef CONFIG_PROC_FS
+static int proc_userns_show(struct seq_file *m, void *v)
+{
+ struct user_namespace *ns = v;
+ seq_printf(m, "userns %p creator (uid %d ns %p) count %d\n",
+ (void *)ns, ns->creator->uid, (void *) ns->creator->user_ns,
+ atomic_read(&ns->kref.refcount));
+ return 0;
+}
+
+static void *proc_userns_start(struct seq_file *p, loff_t *_pos)
+{
+ loff_t pos = *_pos;
+ struct user_namespace *ns = &init_user_ns;
+ spin_lock(&usernslist_lock);
+ while (pos) {
+ pos--;
+ ns = list_entry(ns->list.next, struct user_namespace, list);
+ if (ns == &init_user_ns)
+ return NULL;
+ }
+ return ns;
+}
+
+static void *proc_userns_next(struct seq_file *p, void *v, loff_t *_pos)
+{
+ struct user_namespace *ns = v;
+ (*_pos)++;
+ ns = list_entry(ns->list.next, struct user_namespace, list);
+ if (ns == &init_user_ns)
+ return NULL;
+ return ns;
+}
+
+static void proc_userns_stop(struct seq_file *p, void *v)
+{
+ spin_unlock(&usernslist_lock);
+}
+
+static const struct seq_operations proc_userns_ops;
+
+static int proc_userns_open(struct inode *inode, struct file *filp)
+{
+ return seq_open(filp, &proc_userns_ops);
+}
+
+static const struct seq_operations proc_userns_ops = {
+ .start = proc_userns_start,
+ .next = proc_userns_next,
+ .stop = proc_userns_stop,
+ .show = proc_userns_show,
+};
+
+const struct file_operations proc_userns_fops = {
+ .open = proc_userns_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static __init int user_ns_debug(void)
+{
+ struct proc_dir_entry *p;
+
+ p = proc_create("userns", 0, NULL, &proc_userns_fops);
+ if (!p)
+ panic("cannot create /proc/userns\n");
+ return 0;
+}
+
+__initcall(user_ns_debug);
+#endif
--
1.6.1
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