net: xfrm: unexport __init-annotated xfrm4_protocol_init()

stable inclusion
from stable-4.19.247
commit 31f3c6a4dcd3260a386e62cef2d5b36e902600a1
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5FNPY
CVE: NA

--------------------------------

[ Upstream commit 4a388f08 ]

EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.

modpost used to detect it, but it has been broken for a decade.

Recently, I fixed modpost so it started to warn it again, then this
showed up in linux-next builds.

There are two ways to fix it:

  - Remove __init
  - Remove EXPORT_SYMBOL

I chose the latter for this case because the only in-tree call-site,
net/ipv4/xfrm4_policy.c is never compiled as modular.
(CONFIG_XFRM is boolean)

Fixes: 2f32b51b ("xfrm: Introduce xfrm_input_afinfo to access the the callbacks properly")
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>
Signed-off-by: NLaibin Qiu <qiulaibin@huawei.com>

net/ipv4/xfrm4_protocol.c

@@ -297,4 +297,3 @@ void __init xfrm4_protocol_init(void)
 {
 	xfrm_input_register_afinfo(&xfrm4_input_afinfo);
 }
-EXPORT_SYMBOL(xfrm4_protocol_init);