6.16-stable review patch. If anyone has any objections, please let me know.
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From: Stanislav Fomichev sdf@fomichev.me
[ Upstream commit 0f82c3ba66c6b2e3cde0f255156a753b108ee9dc ]
Syzkaller managed to lock the lower device via ETHTOOL_SFEATURES:
netdev_lock include/linux/netdevice.h:2761 [inline] netdev_lock_ops include/net/netdev_lock.h:42 [inline] netdev_sync_lower_features net/core/dev.c:10649 [inline] __netdev_update_features+0xcb1/0x1be0 net/core/dev.c:10819 netdev_update_features+0x6d/0xe0 net/core/dev.c:10876 macsec_notify+0x2f5/0x660 drivers/net/macsec.c:4533 notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline] call_netdevice_notifiers net/core/dev.c:2281 [inline] netdev_features_change+0x85/0xc0 net/core/dev.c:1570 __dev_ethtool net/ethtool/ioctl.c:3469 [inline] dev_ethtool+0x1536/0x19b0 net/ethtool/ioctl.c:3502 dev_ioctl+0x392/0x1150 net/core/dev_ioctl.c:759
It happens because lower features are out of sync with the upper:
__dev_ethtool (real_dev) netdev_lock_ops(real_dev) ETHTOOL_SFEATURES __netdev_features_change netdev_sync_upper_features disable LRO on the lower if (old_features != dev->features) netdev_features_change fires NETDEV_FEAT_CHANGE macsec_notify NETDEV_FEAT_CHANGE netdev_update_features (for each macsec dev) netdev_sync_lower_features if (upper_features != lower_features) netdev_lock_ops(lower) # lower == real_dev stuck ...
netdev_unlock_ops(real_dev)
Per commit af5f54b0ef9e ("net: Lock lower level devices when updating features"), we elide the lock/unlock when the upper and lower features are synced. Makes sure the lower (real_dev) has proper features after the macsec link has been created. This makes sure we never hit the situation where we need to sync upper flags to the lower.
Reported-by: syzbot+7e0f89fb6cae5d002de0@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7e0f89fb6cae5d002de0 Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations") Signed-off-by: Stanislav Fomichev sdf@fomichev.me Reviewed-by: Sabrina Dubroca sd@queasysnail.net Link: https://patch.msgid.link/20250908173614.3358264-1-sdf@fomichev.me Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/macsec.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c index 01329fe7451a1..0eca96eeed58a 100644 --- a/drivers/net/macsec.c +++ b/drivers/net/macsec.c @@ -4286,6 +4286,7 @@ static int macsec_newlink(struct net_device *dev, if (err < 0) goto del_dev;
+ netdev_update_features(dev); netif_stacked_transfer_operstate(real_dev, dev); linkwatch_fire_event(dev);