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 C1FF429B799; Sat, 30 May 2026 18:12:30 +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=1780164751; cv=none; b=X5mI2bINQ5NINwQalW7IpEbCRWrc5C9ZbB0A6Av73Hm0IUL3ai9b51+EBgJWX5SchPTkQLn/A0IFP5WlFIImluXBN4jdVQg0tMFhMMcOS/RiMAekdwV25Z92PBCO70VVadl/h0P2cHPophgV22kd1TJH6OXpvu+tefk0Ic9kpkQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164751; c=relaxed/simple; bh=rxqzhE53RIoHUbFp3hpl2zCtFvuUxoFzu2y4k1moqww=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PHjvnDRCCLnsjmsS93kDIQRCHxRaH+7DBYEI8j7XMIulT/jIOc3d6TIbyr/PM9kk0f//5zM7XlkzuryRYqMAk3ilcWSfBJpmKEpo2gEyP7UmYfevlpcz+BWSQD8d9PijU0si0wRos+QwH9BMvrDu8BcLtpRQ1siD8gDavmuZkJM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CxkTJ02b; 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="CxkTJ02b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13ABC1F00893; Sat, 30 May 2026 18:12:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780164750; bh=xmmwEV5fR7GiOUo0ymH/i/YQ1Lvxc12UR4m6F8F83qQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=CxkTJ02bPFi0GZlc7RjMhcEmopUs8iW/SL8ucc1pH+6ZKHaqRZGvaDv3XoWC+3KsR 57JskwtqBkqMehbcCrEvbK42SPG7tQrlQi9vAZtl0lhxt9AC0dU9JCSt6vZ0eCHZWv 4kmpOLwL4GOIJLLWurvZPjKyru6G242/zdci378Y= 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 5.15 621/776] vrf: Fix a potential NPD when removing a port from a VRF Date: Sat, 30 May 2026 18:05:35 +0200 Message-ID: <20260530160256.035262946@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160240.228940103@linuxfoundation.org> References: <20260530160240.228940103@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-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 6c719d6da5b82..c0752e8748529 100644 --- a/drivers/net/vrf.c +++ b/drivers/net/vrf.c @@ -1135,6 +1135,7 @@ 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; } @@ -1154,10 +1155,16 @@ 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); @@ -1166,7 +1173,7 @@ 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) @@ -1731,7 +1738,7 @@ 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); @@ -1862,7 +1869,7 @@ 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