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Groups > linux.kernel > #1604962

[PATCH 4.10 41/63] mpls: Do not decrement alive counter for unregister events

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4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Ahern <dsa@cumulusnetworks.com>


[ Upstream commit 79099aab38c8f5c746748b066ae74ba984fe2cc8 ]

Multipath routes can be rendered usesless when a device in one of the
paths is deleted. For example:

$ ip -f mpls ro ls
100
	nexthop as to 200 via inet 172.16.2.2  dev virt12
	nexthop as to 300 via inet 172.16.3.2  dev br0
101
	nexthop as to 201 via inet6 2000:2::2  dev virt12
	nexthop as to 301 via inet6 2000:3::2  dev br0

$ ip li del br0

When br0 is deleted the other hop is not considered in
mpls_select_multipath because of the alive check -- rt_nhn_alive
is 0.

rt_nhn_alive is decremented once in mpls_ifdown when the device is taken
down (NETDEV_DOWN) and again when it is deleted (NETDEV_UNREGISTER). For
a 2 hop route, deleting one device drops the alive count to 0. Since
devices are taken down before unregistering, the decrement on
NETDEV_UNREGISTER is redundant.

Fixes: c89359a42e2a4 ("mpls: support for dead routes")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mpls/af_mpls.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -956,7 +956,8 @@ static void mpls_ifdown(struct net_devic
 				/* fall through */
 			case NETDEV_CHANGE:
 				nh->nh_flags |= RTNH_F_LINKDOWN;
-				ACCESS_ONCE(rt->rt_nhn_alive) = rt->rt_nhn_alive - 1;
+				if (event != NETDEV_UNREGISTER)
+					ACCESS_ONCE(rt->rt_nhn_alive) = rt->rt_nhn_alive - 1;
 				break;
 			}
 			if (event == NETDEV_UNREGISTER)

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[PATCH 4.10 00/63] 4.10.5-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 31/63] net: fix socket refcounting in skb_complete_tx_timestamp() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 33/63] dccp: fix use-after-free in dccp_feat_activate_values Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 32/63] net/sched: act_skbmod: remove unneeded rcu_read_unlock in tcf_skbmod_dump Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 08/63] vti6: return GRE_KEY for vti6 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 07/63] vxlan: correctly validate VXLAN ID against VXLAN_N_VID Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 13/63] net sched actions: decrement module reference count after table flush. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 06/63] sctp: deny peeloff operation on asocs with threads sleeping on it Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 35/63] vrf: Fix use-after-free in vrf_xmit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 16/63] geneve: lock RCU on TX path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 21/63] net: net_enable_timestamp() can be called from irq contexts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 40/63] mpls: Send route delete notifications when router module is unloaded Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 36/63] net/tunnel: set inner protocol in network gro hooks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 29/63] tcp: fix various issues for sockets morphing to listen state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 27/63] bonding: use ETH_MAX_MTU as max mtu Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:10 +0100
  [PATCH 4.10 17/63] mlxsw: spectrum_router: Avoid potential packets loss Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 59/63] futex: Fix potential use-after-free in FUTEX_REQUEUE_PI Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 38/63] amd-xgbe: Enable IRQs only if napi_complete_done() is true Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 60/63] futex: Add missing error handling to FUTEX_REQUEUE_PI Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 22/63] ipv6: orphan skbs in reassembly unit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 56/63] x86/kasan: Fix boot with KASAN=y and PROFILE_ANNOTATED_BRANCHES=y Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 49/63] arm64: KVM: VHE: Clear HCR_TGE when invalidating guest TLBs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 05/63] net/mlx5e: Fix wrong CQE decompression Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 09/63] vxlan: dont allow overwrite of config src addr Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 43/63] ipv6: avoid write to a possibly cloned skb Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 61/63] locking/rwsem: Fix down_write_killable() for CONFIG_RWSEM_GENERIC_SPINLOCK=y Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 41/63] mpls: Do not decrement alive counter for unregister events Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 15/63] vxlan: lock RCU on TX path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 03/63] net/mlx5e: Fix broken CQE compression initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 37/63] uapi: fix linux/packet_diag.h userspace compilation error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 50/63] irqchip/gicv3-its: Add workaround for QDF2400 ITS erratum 0065 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 26/63] amd-xgbe: Dont overwrite SFP PHY mod_absent settings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 12/63] sctp: set sin_port for addr param when checking duplicate address Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 23/63] dccp: Unlock sock before calling sk_free() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 04/63] net/mlx5e: Update MPWQE stride size when modifying CQE compress state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 10/63] ipv4: add missing initialization for flowi4_uid Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 62/63] crypto: powerpc - Fix initialisation of crc32c context Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  [PATCH 4.10 25/63] amd-xgbe: Be sure to set MDIO modes on device (re)start Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-20 19:20 +0100
  Re: [PATCH 4.10 00/63] 4.10.5-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-03-21 01:20 +0100
    Re: [PATCH 4.10 00/63] 4.10.5-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-21 05:40 +0100
  Re: [PATCH 4.10 00/63] 4.10.5-stable review Guenter Roeck <linux@roeck-us.net> - 2017-03-21 03:20 +0100
    Re: [PATCH 4.10 00/63] 4.10.5-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-21 05:50 +0100

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