linux-kernel - [PATCH 4.14 177/218] net: xfrm: unexport __init-annotated xfrm4_protocol

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Message-Id: <20220613094925.975978630@linuxfoundation.org>
Date:   Mon, 13 Jun 2022 12:10:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 177/218] net: xfrm: unexport __init-annotated xfrm4_protocol_init()

From: Masahiro Yamada <masahiroy@...nel.org>

[ Upstream commit 4a388f08d8784af48f352193d2b72aaf167a57a1 ]

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: 2f32b51b609f ("xfrm: Introduce xfrm_input_afinfo to access the the callbacks properly")
Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Acked-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/ipv4/xfrm4_protocol.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv4/xfrm4_protocol.c b/net/ipv4/xfrm4_protocol.c
index 8dd0e6ab8606..0e1f5dc2766b 100644
--- a/net/ipv4/xfrm4_protocol.c
+++ b/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);
-- 
2.35.1