From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C3A203CEB14; Sat, 28 Feb 2026 17:40:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300412; cv=none; b=X1cxV+foDwJAoiAiKOiVOSPJiNNqOf1QYHAD5eeTgCmEpsIssxje9uZ8pxNp1Tndx6cRukGXgcfUkumK9tnNT8/dWpDGX7lvzWH6ZwgoFbtzUcg0n+NSSsPB71G1eIPdVZ86lL16gZxX74MgUO1yEvGuCF0ZZIPdQsJbTj0J0cE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300412; c=relaxed/simple; bh=SrC1HFLWc/goT+GjWOISSRyEcH/2eDN1Im7wikqoMHo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=O2FJ5s2OVlrvxYJR1yubJkMswk4zDJ39VWjUlpt45xKHJrZopbn8cV+fokGm4UfXh1w1vHb7eixAr7v3zaU+O89GhRveHrAd5JJKgFCajSrySuetC53VURQzS7MHWuB86x67NX6QWA7jePm9EFT+MZOFIRo8M55Cx7+Asw/SpnU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j8xjT1xd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="j8xjT1xd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E80C1C116D0; Sat, 28 Feb 2026 17:40:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772300412; bh=SrC1HFLWc/goT+GjWOISSRyEcH/2eDN1Im7wikqoMHo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j8xjT1xdkoF+R02YuJD1nOPrCVjeGxlvWcGBiiwuwR0SAh3dWXjdd2P7nOTA0uSKO aTu3lfGognugZqWEE/bU85WowR7KhJp2jrQfx3H9rYEszDXo+0foRQX4SQwn58eBHE Y2iUwQr5EahU9fSnk9aLqm6DLsCR8mrX4s0g4Aczt51oV/FzE69N7yqRbVUnSnyIGE Hrb6Xig83Dyk/xmakFHbXAYS19Xq36crhZ+B15ZpiIIeyR9y1kPl6nmTx2OsoIWElH rkDxi2TzR0KIagb+pg+1RRSbl3MI90jSHNAsu9S/6JTcLLt6CkmhlVsPmGw3yeZc+v deNfMzVBnu4Hg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Tetsuo Handa , syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com, Sabrina Dubroca , Steffen Klassert , Sasha Levin Subject: [PATCH 6.19 450/844] xfrm: always flush state and policy upon NETDEV_UNREGISTER event Date: Sat, 28 Feb 2026 12:26:03 -0500 Message-ID: <20260228173244.1509663-451-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228173244.1509663-1-sashal@kernel.org> References: <20260228173244.1509663-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Tetsuo Handa [ Upstream commit 4efa91a28576054aae0e6dad9cba8fed8293aef8 ] 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 Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- net/xfrm/xfrm_device.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c index 52ae0e034d29e..550457e4c4f01 100644 --- a/net/xfrm/xfrm_device.c +++ b/net/xfrm/xfrm_device.c @@ -544,6 +544,14 @@ static int xfrm_dev_down(struct net_device *dev) return NOTIFY_DONE; } +static int xfrm_dev_unregister(struct net_device *dev) +{ + xfrm_dev_state_flush(dev_net(dev), dev, true); + xfrm_dev_policy_flush(dev_net(dev), dev, true); + + return NOTIFY_DONE; +} + static int xfrm_dev_event(struct notifier_block *this, unsigned long event, void *ptr) { struct net_device *dev = netdev_notifier_info_to_dev(ptr); @@ -556,8 +564,10 @@ static int xfrm_dev_event(struct notifier_block *this, unsigned long event, void return xfrm_api_check(dev); case NETDEV_DOWN: - case NETDEV_UNREGISTER: return xfrm_dev_down(dev); + + case NETDEV_UNREGISTER: + return xfrm_dev_unregister(dev); } return NOTIFY_DONE; } -- 2.51.0