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 447662D5C68; Tue, 31 Mar 2026 17:00:38 +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=1774976438; cv=none; b=f9Varo4r0LDZcrHl95QzP4HKd1+IZ/FRfXwoxaIu6uYdzH/q0SZlWML2X/LIDRbs0XUb4RGEZT/DWTkLakTjZ26iyFyX2duAJMrCODsAAb3zYY4P6mBU322UDKIfTQyN4PbU+ONH5mzBG7VfObCZ4oLckPidUmS/FYPW8xyLjzE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774976438; c=relaxed/simple; bh=1Ow82+QwkcoxVl8iij/2MXE9J95eb+JJ3xWA7Xy1tjY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=AAK2hdMzHlBwf4oql2jnc26ehm5hFnVFc/CYXCUHBsOHe16sSAdDFKfRBnRScHyiA9Ym5hiAKRLJSplQahmXh0/56sdL8P6vVH3Jz0dRIpad4MDW9tHGJOFHijcsICvpWczQ/5oDwacJgfJZhIxF+ct43jXavrTOhR7qLrINmZk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=stmQ3J5f; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="stmQ3J5f" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEE17C19423; Tue, 31 Mar 2026 17:00:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774976438; bh=1Ow82+QwkcoxVl8iij/2MXE9J95eb+JJ3xWA7Xy1tjY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=stmQ3J5fBizMGNgcR+d1PuX9okJxEPK/dNI2/yhy+N7wG5THTv5ecwGW80o7ZFvLP WuYRlW55F2RfNJq99o3kYUrIQ0X3oLWe3Tfi5oxDKS8wXl9hsVf14pHAl8Tlr3W04k kLI0nJ+CqlurRqriTyRwEfxH0edPu/ygAfrFTH5E= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Minxi Hou , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18 091/309] net: openvswitch: Avoid releasing netdev before teardown completes Date: Tue, 31 Mar 2026 18:19:54 +0200 Message-ID: <20260331161756.841107532@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161753.468533260@linuxfoundation.org> References: <20260331161753.468533260@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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Toke Høiland-Jørgensen [ Upstream commit 7c770dadfda5cbbde6aa3c4363ed513f1d212bf8 ] The patch cited in the Fixes tag below changed the teardown code for OVS ports to no longer unconditionally take the RTNL. After this change, the netdev_destroy() callback can proceed immediately to the call_rcu() invocation if the IFF_OVS_DATAPATH flag is already cleared on the netdev. The ovs_netdev_detach_dev() function clears the flag before completing the unregistration, and if it gets preempted after clearing the flag (as can happen on an -rt kernel), netdev_destroy() can complete and the device can be freed before the unregistration completes. This leads to a splat like: [ 998.393867] Oops: general protection fault, probably for non-canonical address 0xff00000001000239: 0000 [#1] SMP PTI [ 998.393877] CPU: 42 UID: 0 PID: 55177 Comm: ip Kdump: loaded Not tainted 6.12.0-211.1.1.el10_2.x86_64+rt #1 PREEMPT_RT [ 998.393886] Hardware name: Dell Inc. PowerEdge R740/0JMK61, BIOS 2.24.0 03/27/2025 [ 998.393889] RIP: 0010:dev_set_promiscuity+0x8d/0xa0 [ 998.393901] Code: 00 00 75 d8 48 8b 53 08 48 83 ba b0 02 00 00 00 75 ca 48 83 c4 08 5b c3 cc cc cc cc 48 83 bf 48 09 00 00 00 75 91 48 8b 47 08 <48> 83 b8 b0 02 00 00 00 74 97 eb 81 0f 1f 80 00 00 00 00 90 90 90 [ 998.393906] RSP: 0018:ffffce5864a5f6a0 EFLAGS: 00010246 [ 998.393912] RAX: ff00000000ffff89 RBX: ffff894d0adf5a05 RCX: 0000000000000000 [ 998.393917] RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff894d0adf5a05 [ 998.393921] RBP: ffff894d19252000 R08: ffff894d19252000 R09: 0000000000000000 [ 998.393924] R10: ffff894d19252000 R11: ffff894d192521b8 R12: 0000000000000006 [ 998.393927] R13: ffffce5864a5f738 R14: 00000000ffffffe2 R15: 0000000000000000 [ 998.393931] FS: 00007fad61971800(0000) GS:ffff894cc0140000(0000) knlGS:0000000000000000 [ 998.393936] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 998.393940] CR2: 000055df0a2a6e40 CR3: 000000011c7fe003 CR4: 00000000007726f0 [ 998.393944] PKRU: 55555554 [ 998.393946] Call Trace: [ 998.393949] [ 998.393952] ? show_trace_log_lvl+0x1b0/0x2f0 [ 998.393961] ? show_trace_log_lvl+0x1b0/0x2f0 [ 998.393975] ? dp_device_event+0x41/0x80 [openvswitch] [ 998.394009] ? __die_body.cold+0x8/0x12 [ 998.394016] ? die_addr+0x3c/0x60 [ 998.394027] ? exc_general_protection+0x16d/0x390 [ 998.394042] ? asm_exc_general_protection+0x26/0x30 [ 998.394058] ? dev_set_promiscuity+0x8d/0xa0 [ 998.394066] ? ovs_netdev_detach_dev+0x3a/0x80 [openvswitch] [ 998.394092] dp_device_event+0x41/0x80 [openvswitch] [ 998.394102] notifier_call_chain+0x5a/0xd0 [ 998.394106] unregister_netdevice_many_notify+0x51b/0xa60 [ 998.394110] rtnl_dellink+0x169/0x3e0 [ 998.394121] ? rt_mutex_slowlock.constprop.0+0x95/0xd0 [ 998.394125] rtnetlink_rcv_msg+0x142/0x3f0 [ 998.394128] ? avc_has_perm_noaudit+0x69/0xf0 [ 998.394130] ? __pfx_rtnetlink_rcv_msg+0x10/0x10 [ 998.394132] netlink_rcv_skb+0x50/0x100 [ 998.394138] netlink_unicast+0x292/0x3f0 [ 998.394141] netlink_sendmsg+0x21b/0x470 [ 998.394145] ____sys_sendmsg+0x39d/0x3d0 [ 998.394149] ___sys_sendmsg+0x9a/0xe0 [ 998.394156] __sys_sendmsg+0x7a/0xd0 [ 998.394160] do_syscall_64+0x7f/0x170 [ 998.394162] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 998.394165] RIP: 0033:0x7fad61bf4724 [ 998.394188] Code: 89 02 b8 ff ff ff ff eb bb 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 80 3d c5 e9 0c 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89 [ 998.394189] RSP: 002b:00007ffd7e2f7cb8 EFLAGS: 00000202 ORIG_RAX: 000000000000002e [ 998.394191] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fad61bf4724 [ 998.394193] RDX: 0000000000000000 RSI: 00007ffd7e2f7d20 RDI: 0000000000000003 [ 998.394194] RBP: 00007ffd7e2f7d90 R08: 0000000000000010 R09: 000000000000003f [ 998.394195] R10: 000055df11558010 R11: 0000000000000202 R12: 00007ffd7e2f8380 [ 998.394196] R13: 0000000069b233d7 R14: 000055df0a256040 R15: 0000000000000000 [ 998.394200] To fix this, reorder the operations in ovs_netdev_detach_dev() to only clear the flag after completing the other operations, and introduce an smp_wmb() to make the ordering requirement explicit. The smp_wmb() is paired with a full smp_mb() in netdev_destroy() to make sure the call_rcu() invocation does not happen before the unregister operations are visible. Reported-by: Minxi Hou Tested-by: Minxi Hou Fixes: 549822767630 ("net: openvswitch: Avoid needlessly taking the RTNL on vport destroy") Signed-off-by: Toke Høiland-Jørgensen Link: https://patch.msgid.link/20260318155554.1133405-1-toke@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/openvswitch/vport-netdev.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/openvswitch/vport-netdev.c b/net/openvswitch/vport-netdev.c index 6574f9bcdc026..c688dee96503f 100644 --- a/net/openvswitch/vport-netdev.c +++ b/net/openvswitch/vport-netdev.c @@ -151,11 +151,15 @@ static void vport_netdev_free(struct rcu_head *rcu) void ovs_netdev_detach_dev(struct vport *vport) { ASSERT_RTNL(); - vport->dev->priv_flags &= ~IFF_OVS_DATAPATH; netdev_rx_handler_unregister(vport->dev); netdev_upper_dev_unlink(vport->dev, netdev_master_upper_dev_get(vport->dev)); dev_set_promiscuity(vport->dev, -1); + + /* paired with smp_mb() in netdev_destroy() */ + smp_wmb(); + + vport->dev->priv_flags &= ~IFF_OVS_DATAPATH; } static void netdev_destroy(struct vport *vport) @@ -174,6 +178,9 @@ static void netdev_destroy(struct vport *vport) rtnl_unlock(); } + /* paired with smp_wmb() in ovs_netdev_detach_dev() */ + smp_mb(); + call_rcu(&vport->rcu, vport_netdev_free); } -- 2.51.0