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Date: Mon, 15 Aug 2016 13:10:21 -0700
From: Andrei Vagin <avagin@...nvz.org>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: containers@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, Andrei Vagin <avagin@...nvz.org>,
Serge Hallyn <serge.hallyn@...onical.com>,
Kees Cook <keescook@...omium.org>
Subject: [PATCH 1/2] kernel: show current values of user namespace counters
Recently Eric added user namespace counters. User namespace counters is
a feature that allows to limit the number of various kernel objects a
user can create. These limits are set via /proc/sys/user/ sysctls on a
per user namespace basis and are applicable to all users in that
namespace.
This patch adds /proc/PID/userns_counts files to provide current usage
of user namespace counters.
> cat /proc/813/userns_counts
user_namespaces 101000 1
pid_namespaces 101000 1
ipc_namespaces 101000 4
net_namespaces 101000 2
mnt_namespaces 101000 5
mnt_namespaces 100000 1
The meanings of the columns are as follows, from left to right:
Name Object name
UID User ID
Usage Current usage
Cc: Serge Hallyn <serge.hallyn@...onical.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Andrei Vagin <avagin@...nvz.org>
---
fs/proc/array.c | 57 +++++++++++++++++++++++
fs/proc/base.c | 3 ++
fs/proc/internal.h | 1 +
include/linux/user_namespace.h | 8 ++++
kernel/ucount.c | 102 +++++++++++++++++++++++++++++++++++++++++
5 files changed, 171 insertions(+)
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 88c7de1..f186625 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -734,3 +734,60 @@ const struct file_operations proc_tid_children_operations = {
.release = children_seq_release,
};
#endif /* CONFIG_PROC_CHILDREN */
+
+#ifdef CONFIG_USER_NS
+static int ucounts_open(struct inode *inode, struct file *filp)
+{
+ struct ucounts_iterator *iter;
+ struct seq_file *seq;
+ int ret;
+
+ struct task_struct *task;
+ struct user_namespace *ns;
+
+ task = get_proc_task(inode);
+ if (!task)
+ return -ESRCH;
+
+ rcu_read_lock();
+ ns = get_user_ns(__task_cred(task)->user_ns);
+ rcu_read_unlock();
+
+ put_task_struct(task);
+
+ if (ns == NULL)
+ return -ESRCH;
+
+ ret = seq_open_private(filp, &ucounts_seq_operations,
+ sizeof(struct ucounts_iterator));
+
+ if (ret) {
+ put_user_ns(ns);
+ return ret;
+ }
+
+ seq = filp->private_data;
+ iter = seq->private;
+ iter->ns = ns;
+
+ return 0;
+}
+
+int ucounts_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *seq = file->private_data;
+ struct ucounts_iterator *iter = seq->private;
+
+ put_user_ns(iter->ns);
+
+ return seq_release_private(inode, file);
+}
+
+
+const struct file_operations proc_ucounts_operations = {
+ .open = ucounts_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = ucounts_release,
+};
+#endif /* CONFIG_USER_NS */
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 54e2702..4252f7a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2910,6 +2910,9 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("timers", S_IRUGO, proc_timers_operations),
#endif
REG("timerslack_ns", S_IRUGO|S_IWUGO, proc_pid_set_timerslack_ns_operations),
+#ifdef CONFIG_USER_NS
+ REG("userns_counts", S_IRUGO, proc_ucounts_operations),
+#endif
};
static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 7931c55..845cadb 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -298,6 +298,7 @@ extern const struct file_operations proc_pid_smaps_operations;
extern const struct file_operations proc_tid_smaps_operations;
extern const struct file_operations proc_clear_refs_operations;
extern const struct file_operations proc_pagemap_operations;
+extern const struct file_operations proc_ucounts_operations;
extern unsigned long task_vsize(struct mm_struct *);
extern unsigned long task_statm(struct mm_struct *,
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 30ffe10..5f824dd 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -106,6 +106,14 @@ extern ssize_t proc_setgroups_write(struct file *, const char __user *, size_t,
extern int proc_setgroups_show(struct seq_file *m, void *v);
extern bool userns_may_setgroups(const struct user_namespace *ns);
extern bool current_in_userns(const struct user_namespace *target_ns);
+
+struct ucounts_iterator {
+ struct user_namespace *ns;
+ int hash;
+};
+
+extern const struct seq_operations ucounts_seq_operations;
+
#else
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 6ebbe9b..cef09e3 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -9,6 +9,8 @@
#include <linux/sysctl.h>
#include <linux/slab.h>
#include <linux/hash.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
#include <linux/user_namespace.h>
#define UCOUNTS_HASHTABLE_BITS 10
@@ -232,4 +234,104 @@ static __init int user_namespace_sysctl_init(void)
}
subsys_initcall(user_namespace_sysctl_init);
+#ifdef CONFIG_PROC_FS
+static void *ucounts_start(struct seq_file *f, loff_t *pos)
+{
+ struct ucounts_iterator *iter = f->private;
+ int h, i = 0;
+
+ spin_lock(&ucounts_lock);
+ for (h = 0; h < (1 << UCOUNTS_HASHTABLE_BITS); h++) {
+ struct ucounts *ucounts;
+
+ hlist_for_each_entry(ucounts, &ucounts_hashtable[h], node) {
+ if (ucounts->ns != iter->ns)
+ continue;
+ if (i++ < *pos)
+ continue;
+
+ iter->hash = h;
+
+ return ucounts;
+ }
+ }
+
+ return NULL;
+}
+
+static void ucounts_stop(struct seq_file *f, void *v)
+{
+ spin_unlock(&ucounts_lock);
+}
+
+static void *ucounts_next(struct seq_file *f, void *v, loff_t *pos)
+{
+ struct ucounts_iterator *iter = f->private;
+ struct ucounts *ucounts = v;
+ int h;
+
+ ++*pos;
+
+ for (h = iter->hash; h < (1 << UCOUNTS_HASHTABLE_BITS); h++) {
+ struct hlist_node *node;
+
+ if (ucounts == NULL) {
+ node = ucounts_hashtable[h].first;
+ iter->hash = h;
+ } else
+ node = ucounts->node.next;
+
+ ucounts = hlist_entry(node, struct ucounts, node);
+
+ hlist_for_each_entry_from(ucounts, node) {
+ if (ucounts->ns != iter->ns)
+ continue;
+
+ return ucounts;
+ }
+
+ ucounts = NULL;
+ }
+
+ return NULL;
+}
+
+static int ucounts_show(struct seq_file *f, void *v)
+{
+ static const char * const ns_strs[] = {
+ "user_namespaces",
+ "pid_namespaces",
+ "uts_namespaces",
+ "ipc_namespaces",
+ "net_namespaces",
+ "mnt_namespaces",
+ "cgroup_namespaces",
+ NULL
+ };
+ struct user_namespace *ns = current_user_ns();
+ struct ucounts *ucounts = v;
+ uid_t uid;
+ int i;
+
+ uid = from_kuid_munged(ns, ucounts->uid);
+
+ for (i = 0; ns_strs[i]; i++) {
+ int val = atomic_read(&ucounts->ucount[i]);
+
+ if (val == 0)
+ continue;
+
+ seq_printf(f, "%-20s %10u\t%10d\n", ns_strs[i], uid, val);
+ }
+
+ return 0;
+}
+
+const struct seq_operations ucounts_seq_operations = {
+ .start = ucounts_start,
+ .next = ucounts_next,
+ .stop = ucounts_stop,
+ .show = ucounts_show,
+};
+#endif /* CONFIG_PROC_FS */
--
2.5.5
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