linux-kernel - [PATCH 3.16 16/99] crypto: af_alg - Use bh_lock_sock in sk

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Message-ID: <lsq.1589984008.269195898@decadent.org.uk>
Date:   Wed, 20 May 2020 15:13:44 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Eric Dumazet" <eric.dumazet@...il.com>,
        syzbot+c2f1558d49e25cc36e5e@...kaller.appspotmail.com,
        "Herbert Xu" <herbert@...dor.apana.org.au>
Subject: [PATCH 3.16 16/99] crypto: af_alg - Use bh_lock_sock in sk_destruct

3.16.84-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Herbert Xu <herbert@...dor.apana.org.au>

commit 37f96694cf73ba116993a9d2d99ad6a75fa7fdb0 upstream.

As af_alg_release_parent may be called from BH context (most notably
due to an async request that only completes after socket closure,
or as reported here because of an RCU-delayed sk_destruct call), we
must use bh_lock_sock instead of lock_sock.

Reported-by: syzbot+c2f1558d49e25cc36e5e@...kaller.appspotmail.com
Reported-by: Eric Dumazet <eric.dumazet@...il.com>
Fixes: c840ac6af3f8 ("crypto: af_alg - Disallow bind/setkey/...")
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 crypto/af_alg.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -136,11 +136,13 @@ void af_alg_release_parent(struct sock *
 	sk = ask->parent;
 	ask = alg_sk(sk);
 
-	lock_sock(sk);
+	local_bh_disable();
+	bh_lock_sock(sk);
 	ask->nokey_refcnt -= nokey;
 	if (!last)
 		last = !--ask->refcnt;
-	release_sock(sk);
+	bh_unlock_sock(sk);
+	local_bh_enable();
 
 	if (last)
 		sock_put(sk);