[PATCH 3.10 017/319] crypto: algif_skcipher - Fix race condition in skcipher_check_key

From: Willy Tarreau
Date: Sun Feb 05 2017 - 14:16:35 EST


From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
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