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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Ilan Tayari , Guy Shapiro , Yossi Kuperman , Network Development Subject: Re: [PATCH net v2] xfrm: always flush state and policy upon NETDEV_UNREGISTER event Message-ID: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: EXCH-02.secunet.de (10.32.0.172) To EXCH-01.secunet.de (10.32.0.171) On Fri, Jan 30, 2026 at 07:42:47PM +0900, Tetsuo Handa wrote: > syzbot is reporting that "struct xfrm_state" refcount is leaking. > > unregister_netdevice: waiting for netdevsim0 to become free. Usage count = 2 > ref_tracker: netdev@ffff888052f24618 has 1/1 users at > __netdev_tracker_alloc include/linux/netdevice.h:4400 [inline] > netdev_tracker_alloc include/linux/netdevice.h:4412 [inline] > xfrm_dev_state_add+0x3a5/0x1080 net/xfrm/xfrm_device.c:316 > xfrm_state_construct net/xfrm/xfrm_user.c:986 [inline] > xfrm_add_sa+0x34ff/0x5fa0 net/xfrm/xfrm_user.c:1022 > xfrm_user_rcv_msg+0x58e/0xc00 net/xfrm/xfrm_user.c:3507 > netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2550 > xfrm_netlink_rcv+0x71/0x90 net/xfrm/xfrm_user.c:3529 > netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] > netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344 > netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1894 > sock_sendmsg_nosec net/socket.c:727 [inline] > __sock_sendmsg net/socket.c:742 [inline] > ____sys_sendmsg+0xa5d/0xc30 net/socket.c:2592 > ___sys_sendmsg+0x134/0x1d0 net/socket.c:2646 > __sys_sendmsg+0x16d/0x220 net/socket.c:2678 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > This is because commit d77e38e612a0 ("xfrm: Add an IPsec hardware > offloading API") implemented xfrm_dev_unregister() as no-op despite > xfrm_dev_state_add() from xfrm_state_construct() acquires a reference > to "struct net_device". > I guess that that commit expected that NETDEV_DOWN event is fired before > NETDEV_UNREGISTER event fires, and also assumed that xfrm_dev_state_add() > is called only if (dev->features & NETIF_F_HW_ESP) != 0. > > Sabrina Dubroca identified steps to reproduce the same symptoms as below. > > echo 0 > /sys/bus/netdevsim/new_device > dev=$(ls -1 /sys/bus/netdevsim/devices/netdevsim0/net/) > ip xfrm state add src 192.168.13.1 dst 192.168.13.2 proto esp \ > spi 0x1000 mode tunnel aead 'rfc4106(gcm(aes))' $key 128 \ > offload crypto dev $dev dir out > ethtool -K $dev esp-hw-offload off > echo 0 > /sys/bus/netdevsim/del_device > > Like these steps indicate, the NETIF_F_HW_ESP bit can be cleared after > xfrm_dev_state_add() acquired a reference to "struct net_device". > Also, xfrm_dev_state_add() does not check for the NETIF_F_HW_ESP bit > when acquiring a reference to "struct net_device". > > Commit 03891f820c21 ("xfrm: handle NETDEV_UNREGISTER for xfrm device") > re-introduced the NETDEV_UNREGISTER event to xfrm_dev_event(), but that > commit for unknown reason chose to share xfrm_dev_down() between the > NETDEV_DOWN event and the NETDEV_UNREGISTER event. > I guess that that commit missed the behavior in the previous paragraph. > > Therefore, we need to re-introduce xfrm_dev_unregister() in order to > release the reference to "struct net_device" by unconditionally flushing > state and policy. > > Reported-by: syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84 > Fixes: d77e38e612a0 ("xfrm: Add an IPsec hardware offloading API") > Cc: Sabrina Dubroca > Signed-off-by: Tetsuo Handa Now applied to the ipsec tree, thanks a lot!