netdev - [PATCH 3/3] net: ipv6: unexport __init-annotated seg6_hmac

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Date:   Mon,  6 Jun 2022 13:53:55 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        David Ahern <dsahern@...nel.org>,
        David Lebrun <david.lebrun@...ouvain.be>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] net: ipv6: unexport __init-annotated seg6_hmac_init()

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>
---

 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 29bc4e7c3046..6de01185cc68 100644
--- a/net/ipv6/seg6_hmac.c
+++ b/net/ipv6/seg6_hmac.c
@@ -399,7 +399,6 @@ 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)
 {
-- 
2.32.0