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net: initialize init_net earlier

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[ Upstream commit 9c1be1935fb68b2413796cdc03d019b8cf35ab51 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet
2022-02-05 09:01:25 -08:00
committed by Greg Kroah-Hartman
parent 4790998fdd
commit 9c1ace066f
4 changed files with 14 additions and 14 deletions
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3
net/core/dev.c
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@@ -11378,8 +11378,7 @@ 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);
INIT_LIST_HEAD(&net->dev_base_head);
net->dev_name_head = netdev_create_hash();
if (net->dev_name_head == NULL)