Commit 9c1be193 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: initialize init_net earlier 



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]

f8c46cb3 ("netns: do not call pernet ops for not yet set up init_net namespace")
b5082df8 ("net: Initialise init_net.count to 1")
734b6541 ("net: Statically initialize init_net.dev_base_head")

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

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4acc45db

include/net/net_namespace.h

+6 −0
Original line number Diff line number Diff line
@@ -513,4 +513,10 @@ static inline void fnhe_genid_bump(struct net *net) 
	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 */

init/main.c

+2 −0
Original line number Diff line number Diff line
@@ -99,6 +99,7 @@ 
#include <linux/kcsan.h>

#include <linux/init_syscalls.h>

#include <linux/stackdepot.h>

#include <net/net_namespace.h>



#include <asm/io.h>

#include <asm/bugs.h>
@@ -1116,6 +1117,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void) 
	key_init();

	security_init();

	dbg_late_init();

	net_ns_init();

	vfs_caches_init();

	pagecache_init();

	signals_init();

net/core/dev.c

+1 −2
Original line number Diff line number Diff line
@@ -10732,7 +10732,6 @@ static int __net_init netdev_init(struct net *net) 
	BUILD_BUG_ON(GRO_HASH_BUCKETS >

		     8 * sizeof_field(struct napi_struct, gro_bitmask));



	if (net != &init_net)

	INIT_LIST_HEAD(&net->dev_base_head);



	net->dev_name_head = netdev_create_hash();

net/core/net_namespace.c

+5 −12
Original line number Diff line number Diff line
@@ -44,13 +44,7 @@ EXPORT_SYMBOL_GPL(net_rwsem); 
static struct key_tag init_net_key_domain = { .usage = REFCOUNT_INIT(1) };

#endif



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

};

struct net init_net;

EXPORT_SYMBOL(init_net);



static bool init_net_initialized;
@@ -1087,7 +1081,7 @@ static void rtnl_net_notifyid(struct net *net, int cmd, int id, u32 portid, 
	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;
@@ -1108,6 +1102,9 @@ static int __init net_ns_init(void) 


	rcu_assign_pointer(init_net.gen, ng);



#ifdef CONFIG_KEYS

	init_net.key_domain = &init_net_key_domain;

#endif

	down_write(&pernet_ops_rwsem);

	if (setup_net(&init_net, &init_user_ns))

		panic("Could not setup the initial network namespace");
@@ -1122,12 +1119,8 @@ static int __init net_ns_init(void) 
		      RTNL_FLAG_DOIT_UNLOCKED);

	rtnl_register(PF_UNSPEC, RTM_GETNSID, rtnl_net_getid, rtnl_net_dumpid,

		      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)

{

	ops_pre_exit_list(ops, net_exit_list);