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net: initialize init_net earlier

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While testing a patch that will follow later
("net: add netns refcount tracker to struct nsproxy")
I found that devtmpfs_init() was called before init_net
was initialized.

This is a bug, because devtmpfs_setup() calls
ksys_unshare(CLONE_NEWNS);

This has the effect of increasing init_net refcount,
which will be later overwritten to 1, as part of setup_net(&init_net)

We had too many prior patches [1] trying to work around the root cause.

Really, make sure init_net is in BSS section, and that net_ns_init()
is called earlier at boot time.

Note that another patch ("vfs: add netns refcount tracker
to struct fs_context") also will need net_ns_init() being called
before vfs_caches_init()

As a bonus, this patch saves around 4KB in .data section.

[1]

f8c46cb390 ("netns: do not call pernet ops for not yet set up init_net namespace")
b5082df801 ("net: Initialise init_net.count to 1")
734b65417b ("net: Statically initialize init_net.dev_base_head")

v2: fixed a build error reported by kernel build bots (CONFIG_NET=n)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2022-02-05 09:01:25 -08:00 • committed by David S. Miller
parent 4acc45db71
commit 9c1be1935f
4 changed files with 14 additions and 14 deletions
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6
include/net/net_namespace.h
View file

@ -513,4 +513,10 @@ static inline void fnhe_genid_bump(struct net *net)
atomic_inc(&net->fnhe_genid); atomic_inc(&net->fnhe_genid);
} }
#ifdef CONFIG_NET
void net_ns_init(void);
#else
static inline void net_ns_init(void) {}
#endif
#endif /* __NET_NET_NAMESPACE_H */ #endif /* __NET_NET_NAMESPACE_H */

2
init/main.c
View file

@ -99,6 +99,7 @@
#include <linux/kcsan.h> #include <linux/kcsan.h>
#include <linux/init_syscalls.h> #include <linux/init_syscalls.h>
#include <linux/stackdepot.h> #include <linux/stackdepot.h>
#include <net/net_namespace.h>
#include <asm/io.h> #include <asm/io.h>
#include <asm/bugs.h> #include <asm/bugs.h>
@ -1116,6 +1117,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
key_init(); key_init();
security_init(); security_init();
dbg_late_init(); dbg_late_init();
net_ns_init();
vfs_caches_init(); vfs_caches_init();
pagecache_init(); pagecache_init();
signals_init(); signals_init();

3
net/core/dev.c
View file

@ -10732,8 +10732,7 @@ static int __net_init netdev_init(struct net *net)
BUILD_BUG_ON(GRO_HASH_BUCKETS > BUILD_BUG_ON(GRO_HASH_BUCKETS >
8 * sizeof_field(struct napi_struct, gro_bitmask)); 8 * sizeof_field(struct napi_struct, gro_bitmask));
if (net != &init_net) INIT_LIST_HEAD(&net->dev_base_head);
INIT_LIST_HEAD(&net->dev_base_head);
net->dev_name_head = netdev_create_hash(); net->dev_name_head = netdev_create_hash();
if (net->dev_name_head == NULL) if (net->dev_name_head == NULL)

17
net/core/net_namespace.c
View file

@ -44,13 +44,7 @@ EXPORT_SYMBOL_GPL(net_rwsem);
static struct key_tag init_net_key_domain = { .usage = REFCOUNT_INIT(1) }; static struct key_tag init_net_key_domain = { .usage = REFCOUNT_INIT(1) };
#endif #endif
struct net init_net = { struct net init_net;
.ns.count = REFCOUNT_INIT(1),
.dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
#ifdef CONFIG_KEYS
.key_domain = &init_net_key_domain,
#endif
};
EXPORT_SYMBOL(init_net); EXPORT_SYMBOL(init_net);
static bool init_net_initialized; static bool init_net_initialized;
@ -1087,7 +1081,7 @@ out:
rtnl_set_sk_err(net, RTNLGRP_NSID, err); rtnl_set_sk_err(net, RTNLGRP_NSID, err);
} }
static int __init net_ns_init(void) void __init net_ns_init(void)
{ {
struct net_generic *ng; struct net_generic *ng;
@ -1108,6 +1102,9 @@ static int __init net_ns_init(void)
rcu_assign_pointer(init_net.gen, ng); rcu_assign_pointer(init_net.gen, ng);
#ifdef CONFIG_KEYS
init_net.key_domain = &init_net_key_domain;
#endif
down_write(&pernet_ops_rwsem); down_write(&pernet_ops_rwsem);
if (setup_net(&init_net, &init_user_ns)) if (setup_net(&init_net, &init_user_ns))
panic("Could not setup the initial network namespace"); panic("Could not setup the initial network namespace");
@ -1122,12 +1119,8 @@ static int __init net_ns_init(void)
RTNL_FLAG_DOIT_UNLOCKED); RTNL_FLAG_DOIT_UNLOCKED);
rtnl_register(PF_UNSPEC, RTM_GETNSID, rtnl_net_getid, rtnl_net_dumpid, rtnl_register(PF_UNSPEC, RTM_GETNSID, rtnl_net_getid, rtnl_net_dumpid,
RTNL_FLAG_DOIT_UNLOCKED); RTNL_FLAG_DOIT_UNLOCKED);
return 0;
} }
pure_initcall(net_ns_init);
static void free_exit_list(struct pernet_operations *ops, struct list_head *net_exit_list) static void free_exit_list(struct pernet_operations *ops, struct list_head *net_exit_list)
{ {
ops_pre_exit_list(ops, net_exit_list); ops_pre_exit_list(ops, net_exit_list);