From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 2C1943FE37B; Wed, 20 May 2026 18:46:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779302805; cv=none; b=i8U3si1+ePIsWgjDRH/FSFC0HVgsca3MoeCuGRPUgH/nOTtRA+buUPw+6hj++ZjuFRF4lIRTQ6w5pR0QxMco3GCEsvyxZDSwdUrGRcfLUL7frQpgHK6Emek8IQbXAotEBMPHOde9MJ0GdPaoEmLpfVcBE9aHaqP+Xe14jGYMijg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779302805; c=relaxed/simple; bh=e4CnuSpunnfVGnJb6Ucdw61F/HgQeYXb00XgzlDEXMk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PbW68q5CckuA+Ce9qDsoD0z4/KShVJMa/Vifot1JQtN3TpNzLhqBxD9txR5dcuncfFyaKTEwa9RKPWowgyEwCby4bk2fTW/JD1iWXtzoyYQQZ7J6Dz7A1/6ZgDiVlinf7nNuE+9cO19w1dWl/2K4gh8wfTszmf6VKWuucm4LRHI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=AW2UelXy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="AW2UelXy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96A0C1F000E9; Wed, 20 May 2026 18:46:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779302804; bh=WcsX+tSHzZFBVSfcqxDIwXsPZLq0copPxytoE5/JX2g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=AW2UelXyIPvhb+DnuJ0ObQ9XYfCckVdZ257wIyrBBUy4OmX49hsAy0OkSWqJn1FiK dpz1v+lX3mLCzyVObMu0PQNd83mNcX4/WHDRIhybJQSpsn5r+jumt43zD+9BAj3RTm 3kTUaCwPh9bcWjo7eMgWSEqEC6R602r9qfmrSEdE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Haoze Xie , Yifan Wu , Juefei Pu , Yuan Tan , Ido Schimmel , David Ahern , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 389/508] vrf: Fix a potential NPD when removing a port from a VRF Date: Wed, 20 May 2026 18:23:32 +0200 Message-ID: <20260520162107.046089973@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162058.573354582@linuxfoundation.org> References: <20260520162058.573354582@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ido Schimmel [ Upstream commit 2674d603a9e6970463b2b9ebcf8e31e90beae169 ] RCU readers that identified a net device as a VRF port using netif_is_l3_slave() assume that a subsequent call to netdev_master_upper_dev_get_rcu() will return a VRF device. They then continue to dereference its l3mdev operations. This assumption is not always correct and can result in a NPD [1]. There is no RCU synchronization when removing a port from a VRF, so it is possible for an RCU reader to see a new master device (e.g., a bridge) that does not have l3mdev operations. Fix by adding RCU synchronization after clearing the IFF_L3MDEV_SLAVE flag. Skip this synchronization when a net device is removed from a VRF as part of its deletion and when the VRF device itself is deleted. In the latter case an RCU grace period will pass by the time RTNL is released. [1] BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] RIP: 0010:l3mdev_fib_table_rcu (net/l3mdev/l3mdev.c:181) [...] Call Trace: l3mdev_fib_table_by_index (net/l3mdev/l3mdev.c:201 net/l3mdev/l3mdev.c:189) __inet_bind (net/ipv4/af_inet.c:499 (discriminator 3)) inet_bind_sk (net/ipv4/af_inet.c:469) __sys_bind (./include/linux/file.h:62 (discriminator 1) ./include/linux/file.h:83 (discriminator 1) net/socket.c:1951 (discriminator 1)) __x64_sys_bind (net/socket.c:1969 (discriminator 1) net/socket.c:1967 (discriminator 1) net/socket.c:1967 (discriminator 1)) do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1)) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Fixes: fdeea7be88b1 ("net: vrf: Set slave's private flag before linking") Reported-by: Haoze Xie Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Yuan Tan Closes: https://lore.kernel.org/netdev/20260419145332.3988923-1-n05ec@lzu.edu.cn/ Signed-off-by: Ido Schimmel Reviewed-by: David Ahern Link: https://patch.msgid.link/20260423063607.1208202-1-idosch@nvidia.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/vrf.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c index 64114e98d75d0..9f7b05a010519 100644 --- a/drivers/net/vrf.c +++ b/drivers/net/vrf.c @@ -1126,6 +1126,7 @@ static int do_vrf_add_slave(struct net_device *dev, struct net_device *port_dev, err: port_dev->priv_flags &= ~IFF_L3MDEV_SLAVE; + synchronize_net(); return ret; } @@ -1145,10 +1146,16 @@ static int vrf_add_slave(struct net_device *dev, struct net_device *port_dev, } /* inverse of do_vrf_add_slave */ -static int do_vrf_del_slave(struct net_device *dev, struct net_device *port_dev) +static int do_vrf_del_slave(struct net_device *dev, struct net_device *port_dev, + bool needs_sync) { netdev_upper_dev_unlink(port_dev, dev); port_dev->priv_flags &= ~IFF_L3MDEV_SLAVE; + /* Make sure that concurrent RCU readers that identified the device + * as a VRF port see a VRF master or no master at all. + */ + if (needs_sync) + synchronize_net(); cycle_netdev(port_dev, NULL); @@ -1157,7 +1164,7 @@ static int do_vrf_del_slave(struct net_device *dev, struct net_device *port_dev) static int vrf_del_slave(struct net_device *dev, struct net_device *port_dev) { - return do_vrf_del_slave(dev, port_dev); + return do_vrf_del_slave(dev, port_dev, true); } static void vrf_dev_uninit(struct net_device *dev) @@ -1714,7 +1721,7 @@ static void vrf_dellink(struct net_device *dev, struct list_head *head) struct list_head *iter; netdev_for_each_lower_dev(dev, port_dev, iter) - vrf_del_slave(dev, port_dev); + do_vrf_del_slave(dev, port_dev, false); vrf_map_unregister_dev(dev); @@ -1845,7 +1852,7 @@ static int vrf_device_event(struct notifier_block *unused, goto out; vrf_dev = netdev_master_upper_dev_get(dev); - vrf_del_slave(vrf_dev, dev); + do_vrf_del_slave(vrf_dev, dev, false); } out: return NOTIFY_DONE; -- 2.53.0