From cc0f678353027580c09748ef15e0183a37745291 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Mon, 8 Jun 2020 16:48:43 +1000 Subject: [PATCH] crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock() commit 34c86f4c4a7be3b3e35aa48bd18299d4c756064d upstream. The locking in af_alg_release_parent is broken as the BH socket lock can only be taken if there is a code-path to handle the case where the lock is owned by process-context. Instead of adding such handling, we can fix this by changing the ref counts to atomic_t. This patch also modifies the main refcnt to include both normal and nokey sockets. This way we don't have to fudge the nokey ref count when a socket changes from nokey to normal. Credits go to Mauricio Faria de Oliveira who diagnosed this bug and sent a patch for it: https://lore.kernel.org/linux-crypto/20200605161657.535043-1-mfo@canonical.com/ Reported-by: Brian Moyles Reported-by: Mauricio Faria de Oliveira Fixes: 37f96694cf73 ("crypto: af_alg - Use bh_lock_sock in...") Cc: Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- crypto/af_alg.c | 26 +++++++++++--------------- crypto/algif_aead.c | 9 +++------ crypto/algif_hash.c | 9 +++------ crypto/algif_skcipher.c | 9 +++------ include/crypto/if_alg.h | 4 ++-- 5 files changed, 22 insertions(+), 35 deletions(-) diff --git a/crypto/af_alg.c b/crypto/af_alg.c index 3d8e53010cda..a3b9df99af6d 100644 --- a/crypto/af_alg.c +++ b/crypto/af_alg.c @@ -128,21 +128,15 @@ EXPORT_SYMBOL_GPL(af_alg_release); void af_alg_release_parent(struct sock *sk) { struct alg_sock *ask = alg_sk(sk); - unsigned int nokey = ask->nokey_refcnt; - bool last = nokey && !ask->refcnt; + unsigned int nokey = atomic_read(&ask->nokey_refcnt); sk = ask->parent; ask = alg_sk(sk); - local_bh_disable(); - bh_lock_sock(sk); - ask->nokey_refcnt -= nokey; - if (!last) - last = !--ask->refcnt; - bh_unlock_sock(sk); - local_bh_enable(); + if (nokey) + atomic_dec(&ask->nokey_refcnt); - if (last) + if (atomic_dec_and_test(&ask->refcnt)) sock_put(sk); } EXPORT_SYMBOL_GPL(af_alg_release_parent); @@ -187,7 +181,7 @@ static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) err = -EBUSY; lock_sock(sk); - if (ask->refcnt | ask->nokey_refcnt) + if (atomic_read(&ask->refcnt)) goto unlock; swap(ask->type, type); @@ -236,7 +230,7 @@ static int alg_setsockopt(struct socket *sock, int level, int optname, int err = -EBUSY; lock_sock(sk); - if (ask->refcnt) + if (atomic_read(&ask->refcnt) != atomic_read(&ask->nokey_refcnt)) goto unlock; type = ask->type; @@ -301,12 +295,14 @@ int af_alg_accept(struct sock *sk, struct socket *newsock, bool kern) if (err) goto unlock; - if (nokey || !ask->refcnt++) + if (atomic_inc_return_relaxed(&ask->refcnt) == 1) sock_hold(sk); - ask->nokey_refcnt += nokey; + if (nokey) { + atomic_inc(&ask->nokey_refcnt); + atomic_set(&alg_sk(sk2)->nokey_refcnt, 1); + } alg_sk(sk2)->parent = sk; alg_sk(sk2)->type = type; - alg_sk(sk2)->nokey_refcnt = nokey; newsock->ops = type->ops; newsock->state = SS_CONNECTED; diff --git a/crypto/algif_aead.c b/crypto/algif_aead.c index eb1910b6d434..0ae000a61c7f 100644 --- a/crypto/algif_aead.c +++ b/crypto/algif_aead.c @@ -384,7 +384,7 @@ static int aead_check_key(struct socket *sock) struct alg_sock *ask = alg_sk(sk); lock_sock(sk); - if (ask->refcnt) + if (!atomic_read(&ask->nokey_refcnt)) goto unlock_child; psk = ask->parent; @@ -396,11 +396,8 @@ static int aead_check_key(struct socket *sock) if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY) goto unlock; - if (!pask->refcnt++) - sock_hold(psk); - - ask->refcnt = 1; - sock_put(psk); + atomic_dec(&pask->nokey_refcnt); + atomic_set(&ask->nokey_refcnt, 0); err = 0; diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c index 178f4cd75ef1..8673ac8828e9 100644 --- a/crypto/algif_hash.c +++ b/crypto/algif_hash.c @@ -301,7 +301,7 @@ static int hash_check_key(struct socket *sock) struct alg_sock *ask = alg_sk(sk); lock_sock(sk); - if (ask->refcnt) + if (!atomic_read(&ask->nokey_refcnt)) goto unlock_child; psk = ask->parent; @@ -313,11 +313,8 @@ static int hash_check_key(struct socket *sock) if (crypto_ahash_get_flags(tfm) & CRYPTO_TFM_NEED_KEY) goto unlock; - if (!pask->refcnt++) - sock_hold(psk); - - ask->refcnt = 1; - sock_put(psk); + atomic_dec(&pask->nokey_refcnt); + atomic_set(&ask->nokey_refcnt, 0); err = 0; diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c index 4c3bdffe0c3a..ec5567c87a6d 100644 --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -211,7 +211,7 @@ static int skcipher_check_key(struct socket *sock) struct alg_sock *ask = alg_sk(sk); lock_sock(sk); - if (ask->refcnt) + if (!atomic_read(&ask->nokey_refcnt)) goto unlock_child; psk = ask->parent; @@ -223,11 +223,8 @@ static int skcipher_check_key(struct socket *sock) if (crypto_skcipher_get_flags(tfm) & CRYPTO_TFM_NEED_KEY) goto unlock; - if (!pask->refcnt++) - sock_hold(psk); - - ask->refcnt = 1; - sock_put(psk); + atomic_dec(&pask->nokey_refcnt); + atomic_set(&ask->nokey_refcnt, 0); err = 0; diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h index 24cfa96f98ea..864849e942c4 100644 --- a/include/crypto/if_alg.h +++ b/include/crypto/if_alg.h @@ -29,8 +29,8 @@ struct alg_sock { struct sock *parent; - unsigned int refcnt; - unsigned int nokey_refcnt; + atomic_t refcnt; + atomic_t nokey_refcnt; const struct af_alg_type *type; void *private;