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/unix | |
| parent | a123b2f4737a9f4e34e92e502972b6388f90133f (diff) | |
| download | linux-stable-323f0968a81b082cf02ef15b447cd35e4328385e.tar.gz linux-stable-323f0968a81b082cf02ef15b447cd35e4328385e.tar.bz2 linux-stable-323f0968a81b082cf02ef15b447cd35e4328385e.zip | |
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/unix')
| -rw-r--r-- | net/unix/af_unix.c | 34 |
1 files changed, 28 insertions, 6 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index cb9911dcafdb..242d170991b4 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -594,20 +594,42 @@ 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) |