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authorEric Dumazet <edumazet@google.com>2021-09-29 15:57:50 -0700
committerDavid S. Miller <davem@davemloft.net>2021-09-30 14:18:40 +0100
commit35306eb23814444bd4021f8a1c3047d3cb0c8b2b (patch)
treef01ff49d4c08b6e5465f1ad535264518d1885bdc /net/unix
parent656ed8b015f19bf3f6e6b3ddd9a4bb4aa5ca73e1 (diff)
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af_unix: fix races in sk_peer_pid and sk_peer_cred accesses
Jann Horn reported that SO_PEERCRED and SO_PEERGROUPS implementations are racy, as af_unix can concurrently change sk_peer_pid and sk_peer_cred. In order to fix this issue, this patch adds a new spinlock that needs to be used whenever these fields are read or written. Jann also pointed out that l2cap_sock_get_peer_pid_cb() is currently reading sk->sk_peer_pid which makes no sense, as this field is only possibly set by AF_UNIX sockets. We will have to clean this in a separate patch. This could be done by reverting b48596d1dc25 "Bluetooth: L2CAP: Add get_peer_pid callback" or implementing what was truly expected. Fixes: 109f6e39fa07 ("af_unix: Allow SO_PEERCRED to work across namespaces.") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Jann Horn <jannh@google.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Luiz Augusto von Dentz <luiz.von.dentz@intel.com> Cc: Marcel Holtmann <marcel@holtmann.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/unix')
-rw-r--r--net/unix/af_unix.c34
1 files changed, 28 insertions, 6 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f505b89bda6a..efac5989edb5 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -608,20 +608,42 @@ static void unix_release_sock(struct sock *sk, int embrion)
static void init_peercred(struct sock *sk)
{
- put_pid(sk->sk_peer_pid);
- if (sk->sk_peer_cred)
- put_cred(sk->sk_peer_cred);
+ const struct cred *old_cred;
+ struct pid *old_pid;
+
+ spin_lock(&sk->sk_peer_lock);
+ old_pid = sk->sk_peer_pid;
+ old_cred = sk->sk_peer_cred;
sk->sk_peer_pid = get_pid(task_tgid(current));
sk->sk_peer_cred = get_current_cred();
+ spin_unlock(&sk->sk_peer_lock);
+
+ put_pid(old_pid);
+ put_cred(old_cred);
}
static void copy_peercred(struct sock *sk, struct sock *peersk)
{
- put_pid(sk->sk_peer_pid);
- if (sk->sk_peer_cred)
- put_cred(sk->sk_peer_cred);
+ const struct cred *old_cred;
+ struct pid *old_pid;
+
+ if (sk < peersk) {
+ spin_lock(&sk->sk_peer_lock);
+ spin_lock_nested(&peersk->sk_peer_lock, SINGLE_DEPTH_NESTING);
+ } else {
+ spin_lock(&peersk->sk_peer_lock);
+ spin_lock_nested(&sk->sk_peer_lock, SINGLE_DEPTH_NESTING);
+ }
+ old_pid = sk->sk_peer_pid;
+ old_cred = sk->sk_peer_cred;
sk->sk_peer_pid = get_pid(peersk->sk_peer_pid);
sk->sk_peer_cred = get_cred(peersk->sk_peer_cred);
+
+ spin_unlock(&sk->sk_peer_lock);
+ spin_unlock(&peersk->sk_peer_lock);
+
+ put_pid(old_pid);
+ put_cred(old_cred);
}
static int unix_listen(struct socket *sock, int backlog)