Re: [RESEND PATCH net-next 1/6] af_unix: rework unix_maybe_add_creds() to allow sleep

As a preparation for the next patches we need to allow sleeping
in unix_maybe_add_creds() and also return err. Currently, we can't do
that as unix_maybe_add_creds() is being called under unix_state_lock().
There is no need for this, really. So let's move call sites of
this helper a bit and do necessary function signature changes.

Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <redacted>
Cc: Luca Boccassi <redacted>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <redacted>
---
 net/unix/af_unix.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 129388c309b0..6072d89ce2e7 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c

@@ -1955,21 +1955,26 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen
        return err;
 }

-/*
+/* unix_maybe_add_creds() adds current task uid/gid and struct pid to skb if needed.

  */
-static void unix_maybe_add_creds(struct sk_buff *skb, const struct sock *sk,
-                                const struct sock *other)
+static int unix_maybe_add_creds(struct sk_buff *skb, const struct sock *sk,
+                               const struct sock *other)
 {
        if (UNIXCB(skb).pid)
-               return;
+               return 0;

        if (unix_may_passcred(sk) || unix_may_passcred(other)) {
                UNIXCB(skb).pid = get_pid(task_tgid(current));
                current_uid_gid(&UNIXCB(skb).uid, &UNIXCB(skb).gid);
        }
+
+       return 0;
 }

 static bool unix_skb_scm_eq(struct sk_buff *skb,

@@ -2104,6 +2109,10 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
                goto out_sock_put;
        }

+       err = unix_maybe_add_creds(skb, sk, other);
+       if (err)
+               goto out_sock_put;
+
 restart:
        sk_locked = 0;
        unix_state_lock(other);

@@ -2212,7 +2221,6 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
        if (sock_flag(other, SOCK_RCVTSTAMP))
                __net_timestamp(skb);

-       unix_maybe_add_creds(skb, sk, other);
        scm_stat_add(other, skb);
        skb_queue_tail(&other->sk_receive_queue, skb);
        unix_state_unlock(other);

@@ -2256,6 +2264,10 @@ static int queue_oob(struct sock *sk, struct msghdr *msg, struct sock *other,
        if (err < 0)
                goto out;

+       err = unix_maybe_add_creds(skb, sk, other);
+       if (err)
+               goto out;
+
        skb_put(skb, 1);
        err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, 1);

@@ -2275,7 +2287,6 @@ static int queue_oob(struct sock *sk, struct msghdr *msg, struct sock *other,
                goto out_unlock;
        }

-       unix_maybe_add_creds(skb, sk, other);
        scm_stat_add(other, skb);

        spin_lock(&other->sk_receive_queue.lock);

@@ -2369,6 +2380,10 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,

                fds_sent = true;

+               err = unix_maybe_add_creds(skb, sk, other);
+               if (err)
+                       goto out_free;
+
                if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES)) {
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                        err = skb_splice_from_iter(skb, &msg->msg_iter, size,

@@ -2399,7 +2414,6 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
                        goto out_free;
                }

-               unix_maybe_add_creds(skb, sk, other);
                scm_stat_add(other, skb);
                skb_queue_tail(&other->sk_receive_queue, skb);
                unix_state_unlock(other);
--

2.43.0