linux-kernel - [PATCH 3.10 017/319] crypto: algif_skcipher - Fix race condition in skcipher_check

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Message-Id: <1486322063-7558-18-git-send-email-w@1wt.eu>
Date:   Sun,  5 Feb 2017 20:09:21 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 017/319] crypto: algif_skcipher - Fix race condition in skcipher_check_key

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

commit 1822793a523e5d5730b19cc21160ff1717421bc8 upstream.

We need to lock the child socket in skcipher_check_key as otherwise
two simultaneous calls can cause the parent socket to be freed.

Cc: stable@...r.kernel.org
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 crypto/algif_skcipher.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index a7800b7..13fd26e 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -551,22 +551,23 @@ static struct proto_ops algif_skcipher_ops = {
 
 static int skcipher_check_key(struct socket *sock)
 {
-	int err;
+	int err = 0;
 	struct sock *psk;
 	struct alg_sock *pask;
 	struct skcipher_tfm *tfm;
 	struct sock *sk = sock->sk;
 	struct alg_sock *ask = alg_sk(sk);
 
+	lock_sock(sk);
 	if (ask->refcnt)
-		return 0;
+		goto unlock_child;
 
 	psk = ask->parent;
 	pask = alg_sk(ask->parent);
 	tfm = pask->private;
 
 	err = -ENOKEY;
-	lock_sock(psk);
+	lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
 	if (!tfm->has_key)
 		goto unlock;
 
@@ -580,6 +581,8 @@ static int skcipher_check_key(struct socket *sock)
 
 unlock:
 	release_sock(psk);
+unlock_child:
+	release_sock(sk);
 
 	return err;
 }
-- 
2.8.0.rc2.1.gbe9624a