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selftests: net: fib_nexthops: add test for group refcount imbalance bug

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The new selftest runs a sequence which causes circular refcount
dependency between deleted objects which cannot be released and results
in a netdevice refcount imbalance.

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nikolay Aleksandrov 2021-11-22 17:15:14 +02:00 committed by David S. Miller
parent 1005f19b93
commit 02ebe49ab0
1 changed files with 63 additions and 0 deletions
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63
tools/testing/selftests/net/fib_nexthops.sh
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@ -629,6 +629,66 @@ ipv6_fcnal()
log_test $? 0 "Nexthops removed on admin down"
}
ipv6_grp_refs()
{
if [ ! -x "$(command -v mausezahn)" ]; then
echo "SKIP: Could not run test; need mausezahn tool"
return
fi
run_cmd "$IP link set dev veth1 up"
run_cmd "$IP link add veth1.10 link veth1 up type vlan id 10"
run_cmd "$IP link add veth1.20 link veth1 up type vlan id 20"
run_cmd "$IP -6 addr add 2001:db8:91::1/64 dev veth1.10"
run_cmd "$IP -6 addr add 2001:db8:92::1/64 dev veth1.20"
run_cmd "$IP -6 neigh add 2001:db8:91::2 lladdr 00:11:22:33:44:55 dev veth1.10"
run_cmd "$IP -6 neigh add 2001:db8:92::2 lladdr 00:11:22:33:44:55 dev veth1.20"
run_cmd "$IP nexthop add id 100 via 2001:db8:91::2 dev veth1.10"
run_cmd "$IP nexthop add id 101 via 2001:db8:92::2 dev veth1.20"
run_cmd "$IP nexthop add id 102 group 100"
run_cmd "$IP route add 2001:db8:101::1/128 nhid 102"
# create per-cpu dsts through nh 100
run_cmd "ip netns exec me mausezahn -6 veth1.10 -B 2001:db8:101::1 -A 2001:db8:91::1 -c 5 -t tcp "dp=1-1023, flags=syn" >/dev/null 2>&1"
# remove nh 100 from the group to delete the route potentially leaving
# a stale per-cpu dst which holds a reference to the nexthop's net
# device and to the IPv6 route
run_cmd "$IP nexthop replace id 102 group 101"
run_cmd "$IP route del 2001:db8:101::1/128"
# add both nexthops to the group so a reference is taken on them
run_cmd "$IP nexthop replace id 102 group 100/101"
# if the bug described in commit "net: nexthop: release IPv6 per-cpu
# dsts when replacing a nexthop group" exists at this point we have
# an unlinked IPv6 route (but not freed due to stale dst) with a
# reference over the group so we delete the group which will again
# only unlink it due to the route reference
run_cmd "$IP nexthop del id 102"
# delete the nexthop with stale dst, since we have an unlinked
# group with a ref to it and an unlinked IPv6 route with ref to the
# group, the nh will only be unlinked and not freed so the stale dst
# remains forever and we get a net device refcount imbalance
run_cmd "$IP nexthop del id 100"
# if a reference was lost this command will hang because the net device
# cannot be removed
timeout -s KILL 5 ip netns exec me ip link del veth1.10 >/dev/null 2>&1
# we can't cleanup if the command is hung trying to delete the netdev
if [ $? -eq 137 ]; then
return 1
fi
# cleanup
run_cmd "$IP link del veth1.20"
run_cmd "$IP nexthop flush"
return 0
}
ipv6_grp_fcnal()
{
local rc
@ -734,6 +794,9 @@ ipv6_grp_fcnal()
run_cmd "$IP nexthop add id 108 group 31/24"
log_test $? 2 "Nexthop group can not have a blackhole and another nexthop"
ipv6_grp_refs
log_test $? 0 "Nexthop group replace refcounts"
}
ipv6_res_grp_fcnal()