af_packet: allow fanout_add when socket is not RUNNING

PACKET socket can retain its fanout membership through link down and up
and leave a fanout while closed regardless of link state.
However, socket was forbidden from joining a fanout while it was not
RUNNING.

This patch allows PACKET socket to join fanout while not RUNNING.

Socket can be RUNNING if it has a specified protocol. Either directly
from packet_create (being implicitly bound to any interface) or following
a successful bind. Socket RUNNING state is switched off if it is bound to
an interface that went down.

Instead of the test for RUNNING, this patch adds a test that socket can
become RUNNING.

Signed-off-by: Gur Stavi <gur.stavi@huawei.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/4f1a3c37dbef980ef044c4d2adf91c76e2eca14b.1728802323.git.gur.stavi@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f8942062f776ca86b74ee45734b526a944e7894f..2ff4b251842d496a99d05ef3c4a9179ffef96237 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1846,21 +1846,22 @@ static int fanout_add(struct sock *sk, struct fanout_args *args)
        err = -EINVAL;
 
        spin_lock(&po->bind_lock);
-       if (packet_sock_flag(po, PACKET_SOCK_RUNNING) &&
+       if (po->num &&
            match->type == type &&
            match->prot_hook.type == po->prot_hook.type &&
            match->prot_hook.dev == po->prot_hook.dev) {
                err = -ENOSPC;
                if (refcount_read(&match->sk_ref) < match->max_num_members) {
-                       __dev_remove_pack(&po->prot_hook);
-
                        /* Paired with packet_setsockopt(PACKET_FANOUT_DATA) */
                        WRITE_ONCE(po->fanout, match);
 
                        po->rollover = rollover;
                        rollover = NULL;
                        refcount_set(&match->sk_ref, refcount_read(&match->sk_ref) + 1);
-                       __fanout_link(sk, po);
+                       if (packet_sock_flag(po, PACKET_SOCK_RUNNING)) {
+                               __dev_remove_pack(&po->prot_hook);
+                               __fanout_link(sk, po);
+                       }
                        err = 0;
                }
        }