Merge branch 'net-netns-refcount-tracking-base-series'

Eric Dumazet says:

====================
net: netns refcount tracking, base series

We have 100+ syzbot reports about netns being dismantled too soon,
still unresolved as of today.

We think a missing get_net() or an extra put_net() is the root cause.

In order to find the bug(s), and be able to spot future ones,
this patch adds CONFIG_NET_NS_REFCNT_TRACKER and new helpers
to precisely pair all put_net() with corresponding get_net().

To use these helpers, each data structure owning a refcount
should also use a "netns_tracker" to pair the get() and put().

Small sections of codes where the get()/put() are in sight
do not need to have a tracker, because they are short lived,
but in theory it is also possible to declare an on-stack tracker.

v2: Include core networking patches only.
====================

Link: https://lore.kernel.org/r/20211210074426.279563-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2021-12-10 06:38:30 -08:00
commit 3d20408dff
12 changed files with 102 additions and 23 deletions

View File

@ -173,6 +173,7 @@ struct channel {
spinlock_t downl; /* protects `chan', file.xq dequeue */
struct ppp *ppp; /* ppp unit we're connected to */
struct net *chan_net; /* the net channel belongs to */
netns_tracker ns_tracker;
struct list_head clist; /* link in list of channels per unit */
rwlock_t upl; /* protects `ppp' and 'bridge' */
struct channel __rcu *bridge; /* "bridged" ppp channel */
@ -2879,7 +2880,7 @@ int ppp_register_net_channel(struct net *net, struct ppp_channel *chan)
pch->ppp = NULL;
pch->chan = chan;
pch->chan_net = get_net(net);
pch->chan_net = get_net_track(net, &pch->ns_tracker, GFP_KERNEL);
chan->ppp = pch;
init_ppp_file(&pch->file, CHANNEL);
pch->file.hdrlen = chan->hdrlen;
@ -3519,7 +3520,7 @@ ppp_disconnect_channel(struct channel *pch)
*/
static void ppp_destroy_channel(struct channel *pch)
{
put_net(pch->chan_net);
put_net_track(pch->chan_net, &pch->ns_tracker);
pch->chan_net = NULL;
atomic_dec(&channel_count);

View File

@ -61,15 +61,27 @@ static int seq_open_net(struct inode *inode, struct file *file)
}
#ifdef CONFIG_NET_NS
p->net = net;
netns_tracker_alloc(net, &p->ns_tracker, GFP_KERNEL);
#endif
return 0;
}
static void seq_file_net_put_net(struct seq_file *seq)
{
#ifdef CONFIG_NET_NS
struct seq_net_private *priv = seq->private;
put_net_track(priv->net, &priv->ns_tracker);
#else
put_net(&init_net);
#endif
}
static int seq_release_net(struct inode *ino, struct file *f)
{
struct seq_file *seq = f->private_data;
put_net(seq_file_net(seq));
seq_file_net_put_net(seq);
seq_release_private(ino, f);
return 0;
}
@ -87,7 +99,8 @@ int bpf_iter_init_seq_net(void *priv_data, struct bpf_iter_aux_info *aux)
#ifdef CONFIG_NET_NS
struct seq_net_private *p = priv_data;
p->net = get_net(current->nsproxy->net_ns);
p->net = get_net_track(current->nsproxy->net_ns, &p->ns_tracker,
GFP_KERNEL);
#endif
return 0;
}
@ -97,7 +110,7 @@ void bpf_iter_fini_seq_net(void *priv_data)
#ifdef CONFIG_NET_NS
struct seq_net_private *p = priv_data;
put_net(p->net);
put_net_track(p->net, &p->ns_tracker);
#endif
}

View File

@ -48,7 +48,7 @@
#include <uapi/linux/pkt_cls.h>
#include <linux/hashtable.h>
#include <linux/rbtree.h>
#include <linux/ref_tracker.h>
#include <net/net_trackers.h>
struct netpoll_info;
struct device;
@ -300,13 +300,6 @@ enum netdev_state_t {
__LINK_STATE_TESTING,
};
#ifdef CONFIG_NET_DEV_REFCNT_TRACKER
typedef struct ref_tracker *netdevice_tracker;
#else
typedef struct {} netdevice_tracker;
#endif
struct gro_list {
struct list_head list;
int count;

View File

@ -9,7 +9,8 @@ extern struct net init_net;
struct seq_net_private {
#ifdef CONFIG_NET_NS
struct net *net;
struct net *net;
netns_tracker ns_tracker;
#endif
};

View File

@ -34,6 +34,7 @@
#include <net/netns/smc.h>
#include <net/netns/bpf.h>
#include <net/netns/mctp.h>
#include <net/net_trackers.h>
#include <linux/ns_common.h>
#include <linux/idr.h>
#include <linux/skbuff.h>
@ -87,6 +88,7 @@ struct net {
struct idr netns_ids;
struct ns_common ns;
struct ref_tracker_dir refcnt_tracker;
struct list_head dev_base_head;
struct proc_dir_entry *proc_net;
@ -240,6 +242,7 @@ void ipx_unregister_sysctl(void);
#ifdef CONFIG_NET_NS
void __put_net(struct net *net);
/* Try using get_net_track() instead */
static inline struct net *get_net(struct net *net)
{
refcount_inc(&net->ns.count);
@ -258,6 +261,7 @@ static inline struct net *maybe_get_net(struct net *net)
return net;
}
/* Try using put_net_track() instead */
static inline void put_net(struct net *net)
{
if (refcount_dec_and_test(&net->ns.count))
@ -308,6 +312,36 @@ static inline int check_net(const struct net *net)
#endif
static inline void netns_tracker_alloc(struct net *net,
netns_tracker *tracker, gfp_t gfp)
{
#ifdef CONFIG_NET_NS_REFCNT_TRACKER
ref_tracker_alloc(&net->refcnt_tracker, tracker, gfp);
#endif
}
static inline void netns_tracker_free(struct net *net,
netns_tracker *tracker)
{
#ifdef CONFIG_NET_NS_REFCNT_TRACKER
ref_tracker_free(&net->refcnt_tracker, tracker);
#endif
}
static inline struct net *get_net_track(struct net *net,
netns_tracker *tracker, gfp_t gfp)
{
get_net(net);
netns_tracker_alloc(net, tracker, gfp);
return net;
}
static inline void put_net_track(struct net *net, netns_tracker *tracker)
{
netns_tracker_free(net, tracker);
put_net(net);
}
typedef struct {
#ifdef CONFIG_NET_NS
struct net *net;

View File

@ -0,0 +1,18 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __NET_NET_TRACKERS_H
#define __NET_NET_TRACKERS_H
#include <linux/ref_tracker.h>
#ifdef CONFIG_NET_DEV_REFCNT_TRACKER
typedef struct ref_tracker *netdevice_tracker;
#else
typedef struct {} netdevice_tracker;
#endif
#ifdef CONFIG_NET_NS_REFCNT_TRACKER
typedef struct ref_tracker *netns_tracker;
#else
typedef struct {} netns_tracker;
#endif
#endif /* __NET_NET_TRACKERS_H */

View File

@ -202,7 +202,8 @@ struct tcf_exts {
__u32 type; /* for backward compat(TCA_OLD_COMPAT) */
int nr_actions;
struct tc_action **actions;
struct net *net;
struct net *net;
netns_tracker ns_tracker;
#endif
/* Map to export classifier specific extension TLV types to the
* generic extensions API. Unsupported extensions must be set to 0.
@ -218,6 +219,7 @@ static inline int tcf_exts_init(struct tcf_exts *exts, struct net *net,
exts->type = 0;
exts->nr_actions = 0;
exts->net = net;
netns_tracker_alloc(net, &exts->ns_tracker, GFP_KERNEL);
exts->actions = kcalloc(TCA_ACT_MAX_PRIO, sizeof(struct tc_action *),
GFP_KERNEL);
if (!exts->actions)
@ -236,6 +238,8 @@ static inline bool tcf_exts_get_net(struct tcf_exts *exts)
{
#ifdef CONFIG_NET_CLS_ACT
exts->net = maybe_get_net(exts->net);
if (exts->net)
netns_tracker_alloc(exts->net, &exts->ns_tracker, GFP_KERNEL);
return exts->net != NULL;
#else
return true;
@ -246,7 +250,7 @@ static inline void tcf_exts_put_net(struct tcf_exts *exts)
{
#ifdef CONFIG_NET_CLS_ACT
if (exts->net)
put_net(exts->net);
put_net_track(exts->net, &exts->ns_tracker);
#endif
}

View File

@ -350,6 +350,7 @@ struct bpf_local_storage;
* @sk_txtime_deadline_mode: set deadline mode for SO_TXTIME
* @sk_txtime_report_errors: set report errors mode for SO_TXTIME
* @sk_txtime_unused: unused txtime flags
* @ns_tracker: tracker for netns reference
*/
struct sock {
/*
@ -538,6 +539,7 @@ struct sock {
struct bpf_local_storage __rcu *sk_bpf_storage;
#endif
struct rcu_head sk_rcu;
netns_tracker ns_tracker;
};
enum sk_pacing {

View File

@ -8,3 +8,12 @@ config NET_DEV_REFCNT_TRACKER
help
Enable debugging feature to track device references.
This adds memory and cpu costs.
config NET_NS_REFCNT_TRACKER
bool "Enable networking namespace refcount tracking"
depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
select REF_TRACKER
default n
help
Enable debugging feature to track netns references.
This adds memory and cpu costs.

View File

@ -311,6 +311,8 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
LIST_HEAD(net_exit_list);
refcount_set(&net->ns.count, 1);
ref_tracker_dir_init(&net->refcnt_tracker, 128);
refcount_set(&net->passive, 1);
get_random_bytes(&net->hash_mix, sizeof(u32));
preempt_disable();
@ -635,6 +637,7 @@ static DECLARE_WORK(net_cleanup_work, cleanup_net);
void __put_net(struct net *net)
{
ref_tracker_dir_exit(&net->refcnt_tracker);
/* Cleanup the network namespace in process context */
if (llist_add(&net->cleanup_list, &cleanup_list))
queue_work(netns_wq, &net_cleanup_work);

View File

@ -1983,7 +1983,7 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
sock_lock_init(sk);
sk->sk_net_refcnt = kern ? 0 : 1;
if (likely(sk->sk_net_refcnt)) {
get_net(net);
get_net_track(net, &sk->ns_tracker, priority);
sock_inuse_add(net, 1);
}
@ -2039,7 +2039,7 @@ static void __sk_destruct(struct rcu_head *head)
put_pid(sk->sk_peer_pid);
if (likely(sk->sk_net_refcnt))
put_net(sock_net(sk));
put_net_track(sock_net(sk), &sk->ns_tracker);
sk_prot_free(sk->sk_prot_creator, sk);
}
@ -2126,7 +2126,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
/* SANITY */
if (likely(newsk->sk_net_refcnt)) {
get_net(sock_net(newsk));
get_net_track(sock_net(newsk), &newsk->ns_tracker, priority);
sock_inuse_add(sock_net(newsk), 1);
}
sk_node_init(&newsk->sk_node);

View File

@ -32,7 +32,8 @@
static struct dentry *rootdir;
struct l2tp_dfs_seq_data {
struct net *net;
struct net *net;
netns_tracker ns_tracker;
int tunnel_idx; /* current tunnel */
int session_idx; /* index of session within current tunnel */
struct l2tp_tunnel *tunnel;
@ -281,7 +282,7 @@ static int l2tp_dfs_seq_open(struct inode *inode, struct file *file)
rc = PTR_ERR(pd->net);
goto err_free_pd;
}
netns_tracker_alloc(pd->net, &pd->ns_tracker, GFP_KERNEL);
rc = seq_open(file, &l2tp_dfs_seq_ops);
if (rc)
goto err_free_net;
@ -293,7 +294,7 @@ out:
return rc;
err_free_net:
put_net(pd->net);
put_net_track(pd->net, &pd->ns_tracker);
err_free_pd:
kfree(pd);
goto out;
@ -307,7 +308,7 @@ static int l2tp_dfs_seq_release(struct inode *inode, struct file *file)
seq = file->private_data;
pd = seq->private;
if (pd->net)
put_net(pd->net);
put_net_track(pd->net, &pd->ns_tracker);
kfree(pd);
seq_release(inode, file);