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From:   Masahiro Yamada <masahiroy@kernel.org>
To:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org
Cc:     Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        David Ahern <dsahern@kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        linux-kernel@vger.kernel.org
Subject: [PATCH 2/3] net: xfrm: unexport __init-annotated xfrm4_protocol_init()
Date:   Mon,  6 Jun 2022 13:53:54 +0900
Message-Id: <20220606045355.4160711-3-masahiroy@kernel.org>
In-Reply-To: <20220606045355.4160711-1-masahiroy@kernel.org>
References: <20220606045355.4160711-1-masahiroy@kernel.org>
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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@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.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 2fe5860c21d6..b146ce88c5d0 100644
--- a/net/ipv4/xfrm4_protocol.c
+++ b/net/ipv4/xfrm4_protocol.c
@@ -304,4 +304,3 @@ void __init xfrm4_protocol_init(void)
 {
 	xfrm_input_register_afinfo(&xfrm4_input_afinfo);
 }
-EXPORT_SYMBOL(xfrm4_protocol_init);
-- 
2.32.0