[stable,3.10.y,14/18] crypto: algif_skcipher - Fix race condition in skcipher_check_key

Commit Message

Andrey Ryabinin Oct. 27, 2016, 2:29 p.m. UTC

From: Herbert Xu <[e-mail]>

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: [e-mail]
Signed-off-by: Herbert Xu <[e-mail]>
Signed-off-by: Andrey Ryabinin <[e-mail]>
---
 crypto/algif_skcipher.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Patch

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;
 }