From b6743653d134c9ef8436e2db1be1ad4c1e0d0091 Mon Sep 17 00:00:00 2001 From: Xia Yan Date: Thu, 22 Oct 2026 17:08:09 +0800 Subject: [PATCH] macvlan: fix passthru promiscuity accounting while down macvlan_changelink() adjusts the lower device's promiscuity count when NOPROMISC changes, even if the passthru macvlan is down. The reference is acquired in macvlan_open() and released in macvlan_stop(), so a down interface has no reference to change. Clearing NOPROMISC while down leaves an extra reference after the next open/stop cycle. Setting it while down can remove a reference held by another user of the lower device. Guard the count adjustment with netif_running(dev). Keep storing the requested flags while down so the next open uses the new setting. Comparing changelink with open/stop exposed the unmatched count changes; the same issue was also described in earlier macvlan reviews. A netlink test on UML reproduced both DOWN cases before the fix and verified the expected counts afterwards. Repeated flag updates, two open/stop cycles, deletion and bidirectional small-frame delivery were also checked. Full x86_64 builds completed with WERROR disabled for allmodconfig, and WERROR and KASAN disabled for allyesconfig, including the resulting dependency changes. Neither comparison showed new diagnostics. Fixes: df8ef8f3aaa6 ("macvlan: add FDB bridge ops and macvlan flags") Link: https://lore.kernel.org/netdev/179170088566.434549.4699134797461783473@kernel.org/ Link: https://lore.kernel.org/netdev/20261016003009.2692872-1-kuba@kernel.org/ Cc: stable@vger.kernel.org Signed-off-by: Xia Yan Reviewed-by: Hangbin Liu Link: https://patch.msgid.link/20261022090809.12019-1-yanxia@cmss.chinamobile.com Signed-off-by: Jakub Kicinski --- drivers/net/macvlan.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c index afad90b9222a..a48c9e662fe9 100644 --- a/drivers/net/macvlan.c +++ b/drivers/net/macvlan.c @@ -1664,7 +1664,8 @@ static int macvlan_changelink(struct net_device *dev, if (data && data[IFLA_MACVLAN_FLAGS]) { __u16 flags = nla_get_u16(data[IFLA_MACVLAN_FLAGS]); bool promisc = (flags ^ vlan->flags) & MACVLAN_FLAG_NOPROMISC; - if (macvlan_passthru(vlan->port) && promisc) { + if (macvlan_passthru(vlan->port) && promisc && + netif_running(dev)) { int err; if (flags & MACVLAN_FLAG_NOPROMISC)