net: mctp: Consistent peer address handling in ioctl tag allocation

When executing ioctl to allocate tags, if the peer address is 0,
mctp_alloc_local_tag now replaces it with 0xff. However, during tag
dropping, this replacement is not performed, potentially causing the key
not to be dropped as expected.
Signed-off-by: John Wang <wangzhiqiang02@ieisystem.com>
Reviewed-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20240730084636.184140-1-wangzhiqiang02@ieisystem.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mctp/af_mctp.c

@@ -486,6 +486,9 @@ static int mctp_ioctl_droptag(struct mctp_sock *msk, bool tagv2,
 	tag = ctl.tag & MCTP_TAG_MASK;
 	rc = -EINVAL;
 
+	if (ctl.peer_addr == MCTP_ADDR_NULL)
+		ctl.peer_addr = MCTP_ADDR_ANY;
+
 	spin_lock_irqsave(&net->mctp.keys_lock, flags);
 	hlist_for_each_entry_safe(key, tmp, &msk->keys, sklist) {
 		/* we do an irqsave here, even though we know the irq state,