linux-kernel - [PATCH 4.19 243/287] net: ipv6: unexport __init-annotated seg6_hmac

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Message-Id: <20220613094931.384937546@linuxfoundation.org>
Date:   Mon, 13 Jun 2022 12:11:07 +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>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 243/287] net: ipv6: unexport __init-annotated seg6_hmac_init()

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

[ Upstream commit 5801f064e35181c71857a80ff18af4dbec3c5f5c ]

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: bf355b8d2c30 ("ipv6: sr: add core files for SR HMAC support")
Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/ipv6/seg6_hmac.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c
index 8546f94f30d4..a886a8f4c0cb 100644
--- a/net/ipv6/seg6_hmac.c
+++ b/net/ipv6/seg6_hmac.c
@@ -406,7 +406,6 @@ int __init seg6_hmac_init(void)
 {
 	return seg6_hmac_init_algo();
 }
-EXPORT_SYMBOL(seg6_hmac_init);

 int __net_init seg6_hmac_net_init(struct net *net)
 {
-- 
2.35.1