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Subject[PATCH RFC 01/48] Audit: make audit kernel side netlink sock per userns
Date
This patch try to make the audit_sock per user namespace,
not global.

Since sock is assigned to net namespace, when creating
a netns, we will allocate a audit_sock for the userns
which create this netns, and this netns will keep alive
until the creator userns being destroyed.

If userns create many netns, the audit_sock is only
allocated once.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
---
include/linux/audit.h | 5 +++
include/linux/user_namespace.h | 9 ++++++
kernel/audit.c | 73 ++++++++++++++++++++++++++++++++++--------
kernel/user_namespace.c | 2 ++
4 files changed, 75 insertions(+), 14 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 5a6d718..690d7d8 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -429,6 +429,8 @@ static inline void audit_log_secctx(struct audit_buffer *ab, u32 secid)
{ }
#endif

+extern void audit_free_user_ns(struct user_namespace *ns);
+
extern int audit_update_lsm_rules(void);

/* Private API (for audit.c only) */
@@ -476,6 +478,9 @@ static inline void audit_log_link_denied(const char *string,
{ }
static inline void audit_log_secctx(struct audit_buffer *ab, u32 secid)
{ }
+
+static inline void audit_free_user_ns(struct user_namespace *ns)
+{ }
#define audit_enabled 0
#endif /* CONFIG_AUDIT */
static inline void audit_log_string(struct audit_buffer *ab, const char *buf)
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index b6b215f..8797421 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -17,6 +17,12 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
} extent[UID_GID_MAP_MAX_EXTENTS];
};

+#ifdef CONFIG_AUDIT
+struct audit_ctrl {
+ struct sock *sock;
+};
+#endif
+
struct user_namespace {
struct uid_gid_map uid_map;
struct uid_gid_map gid_map;
@@ -26,6 +32,9 @@ struct user_namespace {
kuid_t owner;
kgid_t group;
unsigned int proc_inum;
+#ifdef CONFIG_AUDIT
+ struct audit_ctrl audit;
+#endif
bool may_mount_sysfs;
bool may_mount_proc;
};
diff --git a/kernel/audit.c b/kernel/audit.c
index 0b084fa..766dcbf 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -62,6 +62,7 @@
#include <linux/freezer.h>
#include <linux/tty.h>
#include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>

#include "audit.h"

@@ -118,9 +119,6 @@ u32 audit_sig_sid = 0;
*/
static atomic_t audit_lost = ATOMIC_INIT(0);

-/* The netlink socket. */
-static struct sock *audit_sock;
-
/* Hash for inode-based rules */
struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS];

@@ -404,7 +402,8 @@ static void kauditd_send_skb(struct sk_buff *skb)
int err;
/* take a reference in case we can't send it and we want to hold it */
skb_get(skb);
- err = netlink_unicast(audit_sock, skb, audit_nlk_portid, 0);
+ err = netlink_unicast(init_user_ns.audit.sock, skb,
+ audit_nlk_portid, 0);
if (err < 0) {
BUG_ON(err != -ECONNREFUSED); /* Shouldn't happen */
printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
@@ -481,7 +480,7 @@ int audit_send_list(void *_dest)
mutex_unlock(&audit_cmd_mutex);

while ((skb = __skb_dequeue(&dest->q)) != NULL)
- netlink_unicast(audit_sock, skb, pid, 0);
+ netlink_unicast(init_user_ns.audit.sock, skb, pid, 0);

kfree(dest);

@@ -522,7 +521,8 @@ static int audit_send_reply_thread(void *arg)

/* Ignore failure. It'll only happen if the sender goes away,
because our timeout is set to infinite. */
- netlink_unicast(audit_sock, reply->skb, reply->pid, 0);
+ netlink_unicast(init_user_ns.audit.sock, reply->skb,
+ reply->pid, 0);
kfree(reply);
return 0;
}
@@ -937,24 +937,56 @@ static void audit_receive(struct sk_buff *skb)
mutex_unlock(&audit_cmd_mutex);
}

+static int __net_init audit_net_init(struct net *net)
+{
+ struct user_namespace *ns = net->user_ns;
+
+ if (!ns->audit.sock) {
+ struct sock *sk = NULL;
+ /*
+ * create kernel side netlink socket for audit,
+ * make audit sock per user namespace.
+ */
+ struct netlink_kernel_cfg cfg = {
+ .input = audit_receive,
+ };
+
+ sk = netlink_kernel_create(net, NETLINK_AUDIT, &cfg);
+ if (!sk) {
+ if (net_eq(net, &init_net))
+ audit_panic("cannot initialize netlink socket");
+ return -1;
+ }
+ sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
+ ns->audit.sock = sk;
+ /*
+ * Get reference of net->passive, this force this netns
+ * to be alive, it will be destroyed when we destroy the
+ * userns.
+ */
+ atomic_inc(&net->passive);
+ }
+
+ return 0;
+}
+
+static struct pernet_operations audit_net_ops = {
+ .init = audit_net_init,
+};
+
/* Initialize audit support at boot time. */
static int __init audit_init(void)
{
int i;
- struct netlink_kernel_cfg cfg = {
- .input = audit_receive,
- };

if (audit_initialized == AUDIT_DISABLED)
return 0;

printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
audit_default ? "enabled" : "disabled");
- audit_sock = netlink_kernel_create(&init_net, NETLINK_AUDIT, &cfg);
- if (!audit_sock)
- audit_panic("cannot initialize netlink socket");
- else
- audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
+
+ if (register_pernet_subsys(&audit_net_ops) < 0)
+ return -1;

skb_queue_head_init(&audit_skb_queue);
skb_queue_head_init(&audit_skb_hold_queue);
@@ -1549,7 +1581,20 @@ void audit_log_secctx(struct audit_buffer *ab, u32 secid)
EXPORT_SYMBOL(audit_log_secctx);
#endif

+void audit_free_user_ns(struct user_namespace *ns)
+{
+ if (audit_initialized == AUDIT_DISABLED)
+ return;
+
+ if (ns->audit.sock) {
+ struct net *net = sock_net(ns->audit.sock);
+ netlink_kernel_release(ns->audit.sock);
+ net_drop_ns(net);
+ }
+}
+
EXPORT_SYMBOL(audit_log_start);
EXPORT_SYMBOL(audit_log_end);
EXPORT_SYMBOL(audit_log_format);
EXPORT_SYMBOL(audit_log);
+EXPORT_SYMBOL(audit_free_user_ns);
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index d8c30db..99de920 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -22,6 +22,7 @@
#include <linux/ctype.h>
#include <linux/projid.h>
#include <linux/fs_struct.h>
+#include <linux/audit.h>

static struct kmem_cache *user_ns_cachep __read_mostly;

@@ -124,6 +125,7 @@ void free_user_ns(struct user_namespace *ns)
do {
parent = ns->parent;
proc_free_inum(ns->proc_inum);
+ audit_free_user_ns(ns);
kmem_cache_free(user_ns_cachep, ns);
ns = parent;
} while (atomic_dec_and_test(&parent->count));
--
1.8.1.4


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