diff options
| author | Eric Dumazet <edumazet@google.com> | 2021-09-29 15:57:50 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-10-09 13:24:30 +0200 |
| commit | 323f0968a81b082cf02ef15b447cd35e4328385e (patch) | |
| tree | 59f0c2292cb9f0912781afc4e4b74e82433a2947 /net/core/sock.c | |
| parent | a123b2f4737a9f4e34e92e502972b6388f90133f (diff) | |
af_unix: fix races in sk_peer_pid and sk_peer_cred accesses
commit 35306eb23814444bd4021f8a1c3047d3cb0c8b2b upstream.
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>
[backport note: 4.4 and 4.9 don't have SO_PEERGROUPS, only SO_PEERCRED]
[backport note: got rid of sk_get_peer_cred(), no users in 4.4/4.9]
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/core/sock.c')
| -rw-r--r-- | net/core/sock.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/net/core/sock.c b/net/core/sock.c index 82f9a7dbea6f..5e9ff8d9f9e3 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1014,7 +1014,6 @@ set_rcvbuf: } EXPORT_SYMBOL(sock_setsockopt); - static void cred_to_ucred(struct pid *pid, const struct cred *cred, struct ucred *ucred) { @@ -1174,7 +1173,11 @@ int sock_getsockopt(struct socket *sock, int level, int optname, struct ucred peercred; if (len > sizeof(peercred)) len = sizeof(peercred); + + spin_lock(&sk->sk_peer_lock); cred_to_ucred(sk->sk_peer_pid, sk->sk_peer_cred, &peercred); + spin_unlock(&sk->sk_peer_lock); + if (copy_to_user(optval, &peercred, len)) return -EFAULT; goto lenout; @@ -1467,9 +1470,10 @@ void sk_destruct(struct sock *sk) sk->sk_frag.page = NULL; } - if (sk->sk_peer_cred) - put_cred(sk->sk_peer_cred); + /* We do not need to acquire sk->sk_peer_lock, we are the last user. */ + put_cred(sk->sk_peer_cred); put_pid(sk->sk_peer_pid); + if (likely(sk->sk_net_refcnt)) put_net(sock_net(sk)); sk_prot_free(sk->sk_prot_creator, sk); @@ -2442,6 +2446,8 @@ void sock_init_data(struct socket *sock, struct sock *sk) sk->sk_peer_pid = NULL; sk->sk_peer_cred = NULL; + spin_lock_init(&sk->sk_peer_lock); + sk->sk_write_pending = 0; sk->sk_rcvlowat = 1; sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT; |