net: ipv6: unexport __init-annotated seg6_hmac_init()

stable inclusion
from stable-v5.10.122
commit 5d9c1b081ad28c852a97e10dd75412546497694a
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5W6OE

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5d9c1b081ad28c852a97e10dd75412546497694a



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[ Upstream commit 5801f064 ]

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 caller (net/ipv6/seg6.c)
and the callee (net/ipv6/seg6_hmac.c) belong to the same module.
It seems an internal function call in ipv6.ko.

Fixes: bf355b8d ("ipv6: sr: add core files for SR HMAC support")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>