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authorHerbert Xu <herbert@gondor.apana.org.au>2020-06-08 16:48:43 +1000
committerHerbert Xu <herbert@gondor.apana.org.au>2020-06-18 17:09:54 +1000
commit34c86f4c4a7be3b3e35aa48bd18299d4c756064d (patch)
treef228827d837f16799bbab27d118d1f1fd373c799 /crypto/af_alg.c
parent819966c06b759022e9932f328284314d9272b9f3 (diff)
crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock()
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 <bmoyles@netflix.com> Reported-by: Mauricio Faria de Oliveira <mfo@canonical.com> Fixes: 37f96694cf73 ("crypto: af_alg - Use bh_lock_sock in...") Cc: <stable@vger.kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/af_alg.c')
-rw-r--r--crypto/af_alg.c26
1 files changed, 11 insertions, 15 deletions
diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index b1cd3535c525..28fc323e3fe3 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;