linux-kernel - Re: [GIT] Networking

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Date:   Mon, 10 Jul 2017 22:00:48 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:     David Miller <davem@...emloft.net>, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Miloslav Trmač <mitr@...hat.com>
Subject: Re: [GIT] Networking

On Mon, Jul 10, 2017 at 08:10:02AM -0400, Sowmini Varadhan wrote:
>
> The reason that the WARN_ON is triggered is that af_alg_accept() calls
> sock_init_data() which does 
> 
>    2636         if (sock) {
>     :
>    2639                 sock->sk        =       sk;

Oh yes.  This started out with just sock_init_data which would
not have triggered your warning.  Then someone came along and
added sock_graft which basically duplicates work already done in
sock_init_data.

In fact the reason they wanted sock_graft was purely to call
security_sock_graft to initialise some SELinux state.  So we
could avoid your warning by calling that directly.

---8<---
crypto: af_alg - Avoid sock_graft call warning

The newly added sock_graft warning triggers in af_alg_accept.
It's harmless as we're essentially doing sock->sk = sock->sk.

The sock_graft call is actually redundant because all the work
it does is subsumed by sock_init_data.  However, it was added
to placate SELinux as it uses it to initialise its internal state.

This patch avoisd the warning by making the SELinux call directly.

Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 3556d8e..92a3d54 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -287,7 +287,7 @@ int af_alg_accept(struct sock *sk, struct socket *newsock, bool kern)
 		goto unlock;

 	sock_init_data(newsock, sk2);
-	sock_graft(sk2, newsock);
+	security_sock_graft(sk2, newsock);
 	security_sk_clone(sk, sk2);

 	err = type->accept(ask->private, sk2);
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt