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net: add networking namespace refcount tracker

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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.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet
2021-12-09 23:44:21 -08:00
committed by Jakub Kicinski
parent e5d75fc20b
commit 9ba74e6c9e
5 changed files with 65 additions and 8 deletions
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34
include/net/net_namespace.h
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;