Thanks for the quick feedback, Aaron. Right -- the test exercises the SET-without-actions code path but does not force the allocation failure that triggers the actual kfree_skb of ERR_PTR. The crash needs both conditions: (1) SET without actions, and (2) ovs_flow_cmd_build_info() returning ERR_PTR due to memory pressure. Without (2), reply allocation succeeds and kfree_skb() frees a normal skb, so no splat even on an unpatched kernel.
Forcing allocation failure in a selftest would require fault injection (failslab or similar), which felt too fragile for kselftest. So this test is functional coverage for OVS_FLOW_CMD_SET. It verifies the no-actions path works correctly (actions preserved, no crash under normal conditions), not a crash reproducer. Regarding the fix ordering: Adrian's patch targets net, so it should flow into net-next through the regular merge before this selftest lands. Happy to add a comment in the test noting the dependency if you think that would help. Will wait for your deeper review on Monday. Also sending a v2 shortly to fix two pylint warnings that nipa flagged (+2 new warnings: missing docstring on mod_flow, and a %-format string). Aaron Conole <[email protected]> 于2026年6月6日周六 02:51写道： > Minxi Hou <[email protected]> writes: > > > Add mod_flow() and the mod-flow CLI command to ovs-dpctl.py, exercising > > OVS_FLOW_CMD_SET. Add test_flow_set which first modifies an existing > > flow with new actions and verifies the change via traffic, then modifies > > the same flow without actions and verifies the kernel handles the > > no-actions case gracefully. > > > > The no-actions path is unreachable from userspace OVS tools (dpctl > > mod-flow requires actions) but reachable via raw netlink. This is the > > code path where Adrian Moreno found a possible kfree_skb of ERR_PTR > > when reply allocation fails after locking. > > > > Make parse() skip OVS_FLOW_ATTR_ACTIONS when actstr is None so the > > kernel enters the post-lock allocation branch in ovs_flow_cmd_set(). > > > > Suggested-by: Aaron Conole <[email protected]> > > Signed-off-by: Minxi Hou <[email protected]> > > --- > > Thanks for the really quick turnaround. I'll do a deeper review of the > code on Monday; I wanted to reply though because I was expecting to see > a splat in the selftest, but instead it passed. This confused me at > first, because I didn't realize that the net- targeted patches were also > applied in the net-next test run: > > > https://github.com/linux-netdev/testing/commit/30e78e3cb99d9abb5182c387abdf5ede29fb9589 > ("net: openvswitch: fix possible kfree_skb of ERR_PTR") > > But we will want to make sure that whenever this selftest would finally > get applied the above kfree_skb fix is also applied. > > > .../selftests/net/openvswitch/openvswitch.sh | 72 +++++++++++++++++++ > > .../selftests/net/openvswitch/ovs-dpctl.py | 39 +++++++++- > > 2 files changed, 108 insertions(+), 3 deletions(-) > > > > diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh > b/tools/testing/selftests/net/openvswitch/openvswitch.sh > > index a415e9dec8cd..71190bc662f9 100755 > > --- a/tools/testing/selftests/net/openvswitch/openvswitch.sh > > +++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh > > @@ -30,6 +30,7 @@ tests=" > > drop_reason drop: test drop reasons > are emitted > > pop_vlan vlan: POP_VLAN action > strips tag > > dec_ttl ttl: dec_ttl decrements IP > TTL > > + flow_set flow-set: Flow modify > > psample psample: Sampling packets > with psample" > > > > info() { > > @@ -193,6 +194,23 @@ ovs_add_flow () { > > return 0 > > } > > > > +ovs_mod_flow () { > > + if [ -n "$4" ]; then > > + info "Modifying flow: sbx:$1 br:$2 flow:$3 act:$4" > > + ovs_sbx "$1" python3 $ovs_base/ovs-dpctl.py \ > > + mod-flow "$2" "$3" "$4" > > + else > > + info "Modifying flow (no actions): sbx:$1 br:$2 flow:$3" > > + ovs_sbx "$1" python3 $ovs_base/ovs-dpctl.py \ > > + mod-flow "$2" "$3" > > + fi > > + if [ $? -ne 0 ]; then > > + info "Flow modify [ $3 ] failed" > > + return 1 > > + fi > > + return 0 > > +} > > + > > ovs_del_flows () { > > info "Deleting all flows from DP: sbx:$1 br:$2" > > ovs_sbx "$1" python3 $ovs_base/ovs-dpctl.py del-flows "$2" > > @@ -300,6 +318,60 @@ test_dec_ttl() { > > return 0 > > } > > > > +test_flow_set() { > > + sbx_add "test_flow_set" || return $? > > + ovs_add_dp "test_flow_set" flowset || return 1 > > + > > + info "create namespaces" > > + for ns in client server; do > > + ovs_add_netns_and_veths "test_flow_set" "flowset" "$ns" \ > > + "${ns:0:1}0" "${ns:0:1}1" || return 1 > > + done > > + > > + ip netns exec client ip addr add 10.0.0.1/24 dev c1 > > + ip netns exec client ip link set c1 up > > + ip netns exec server ip addr add 10.0.0.2/24 dev s1 > > + ip netns exec server ip link set s1 up > > + > > + ovs_add_flow "test_flow_set" flowset \ > > + 'in_port(1),eth(),eth_type(0x0806),arp()' '2' || return 1 > > + ovs_add_flow "test_flow_set" flowset \ > > + 'in_port(2),eth(),eth_type(0x0806),arp()' '1' || return 1 > > + > > + local fwd_flow="ufid:00000001-0002-0003-0004-000500060007" > > + fwd_flow="$fwd_flow,in_port(1),eth(),eth_type(0x0800),ipv4()" > > + > > + ovs_add_flow "test_flow_set" flowset "$fwd_flow" '2' \ > > + || return 1 > > + ovs_add_flow "test_flow_set" flowset \ > > + 'in_port(2),eth(),eth_type(0x0800),ipv4()' '1' || return 1 > > + > > + info "verify initial forwarding" > > + ovs_sbx "test_flow_set" ip netns exec client ping -c 1 -W 2 \ > > + 10.0.0.2 || return 1 > > + > > + info "mod-flow with new actions (change to drop)" > > + ovs_mod_flow "test_flow_set" flowset "$fwd_flow" 'drop' \ > > + || return 1 > > + > > + info "verify traffic is now dropped" > > + ovs_sbx "test_flow_set" ip netns exec client ping -c 1 -W 2 \ > > + 10.0.0.2 >/dev/null 2>&1 \ > > + && { info "FAIL: ping should fail after mod-flow to drop" > > + return 1; } > > + > > + info "mod-flow without actions" > > + ovs_mod_flow "test_flow_set" flowset "$fwd_flow" || return 1 > > + > > + info "verify drop actions unchanged" > > + ovs_sbx "test_flow_set" ip netns exec client ping -c 1 -W 2 \ > > + 10.0.0.2 >/dev/null 2>&1 \ > > + && { info "FAIL: ping should still fail after no-actions > set" > > + return 1; } > > + > > + return 0 > > +} > > + > > # psample test > > # - use psample to observe packets > > test_psample() { > > diff --git a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py > b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py > > index 3342e295293d..9113473d425f 100644 > > --- a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py > > +++ b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py > > @@ -2702,9 +2702,10 @@ class OvsFlow(GenericNetlinkSocket): > > self["attrs"].append(["OVS_FLOW_ATTR_KEY", k]) > > self["attrs"].append(["OVS_FLOW_ATTR_MASK", m]) > > > > - a = ovsactions() > > - a.parse(actstr) > > - self["attrs"].append(["OVS_FLOW_ATTR_ACTIONS", a]) > > + if actstr is not None: > > + a = ovsactions() > > + a.parse(actstr) > > + self["attrs"].append(["OVS_FLOW_ATTR_ACTIONS", a]) > > > > def __init__(self): > > GenericNetlinkSocket.__init__(self) > > @@ -2738,6 +2739,24 @@ class OvsFlow(GenericNetlinkSocket): > > raise ne > > return reply > > > > + def mod_flow(self, dpifindex, flowmsg): > > + flowmsg["cmd"] = OVS_FLOW_CMD_SET > > + flowmsg["version"] = OVS_DATAPATH_VERSION > > + flowmsg["reserved"] = 0 > > + flowmsg["dpifindex"] = dpifindex > > + > > + try: > > + reply = self.nlm_request( > > + flowmsg, > > + msg_type=self.prid, > > + msg_flags=NLM_F_REQUEST | NLM_F_ACK, > > + ) > > + reply = reply[0] > > + except NetlinkError as ne: > > + print(flowmsg) > > + raise ne > > + return reply > > + > > def del_flows(self, dpifindex): > > """ > > Send a del message to the kernel that will drop all flows. > > @@ -3013,6 +3032,12 @@ def main(argv): > > addflcmd.add_argument("flow", help="Flow specification") > > addflcmd.add_argument("acts", help="Flow actions") > > > > + modflcmd = subparsers.add_parser("mod-flow") > > + modflcmd.add_argument("modbr", help="Datapath name") > > + modflcmd.add_argument("modflow", help="Flow specification") > > + modflcmd.add_argument("modacts", help="Flow actions", > > + nargs="?", default=None) > > + > > delfscmd = subparsers.add_parser("del-flows") > > delfscmd.add_argument("flsbr", help="Datapath name") > > > > @@ -3110,6 +3135,14 @@ def main(argv): > > flow = OvsFlow.ovs_flow_msg() > > flow.parse(args.flow, args.acts, rep["dpifindex"]) > > ovsflow.add_flow(rep["dpifindex"], flow) > > + elif hasattr(args, "modbr"): > > + rep = ovsdp.info(args.modbr, 0) > > + if rep is None: > > + print("DP '%s' not found." % args.modbr) > > + return 1 > > + flow = OvsFlow.ovs_flow_msg() > > + flow.parse(args.modflow, args.modacts, rep["dpifindex"]) > > + ovsflow.mod_flow(rep["dpifindex"], flow) > > elif hasattr(args, "flsbr"): > > rep = ovsdp.info(args.flsbr, 0) > > if rep is None: > > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
