From 6e2f90d31fe09f2b852de25125ca875aabd81367 Mon Sep 17 00:00:00 2001 From: Aaron Conole Date: Wed, 7 Feb 2024 08:24:15 -0500 Subject: [PATCH 1/2] net: openvswitch: limit the number of recursions from action sets The ovs module allows for some actions to recursively contain an action list for complex scenarios, such as sampling, checking lengths, etc. When these actions are copied into the internal flow table, they are evaluated to validate that such actions make sense, and these calls happen recursively. The ovs-vswitchd userspace won't emit more than 16 recursion levels deep. However, the module has no such limit and will happily accept limits larger than 16 levels nested. Prevent this by tracking the number of recursions happening and manually limiting it to 16 levels nested. The initial implementation of the sample action would track this depth and prevent more than 3 levels of recursion, but this was removed to support the clone use case, rather than limited at the current userspace limit. Fixes: 798c166173ff ("openvswitch: Optimize sample action for the clone use cases") Signed-off-by: Aaron Conole Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20240207132416.1488485-2-aconole@redhat.com Signed-off-by: Jakub Kicinski --- net/openvswitch/flow_netlink.c | 49 +++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 16 deletions(-) diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c index 88965e2068ac6..ebc5728aab4ea 100644 --- a/net/openvswitch/flow_netlink.c +++ b/net/openvswitch/flow_netlink.c @@ -48,6 +48,7 @@ struct ovs_len_tbl { #define OVS_ATTR_NESTED -1 #define OVS_ATTR_VARIABLE -2 +#define OVS_COPY_ACTIONS_MAX_DEPTH 16 static bool actions_may_change_flow(const struct nlattr *actions) { @@ -2545,13 +2546,15 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, const struct sw_flow_key *key, struct sw_flow_actions **sfa, __be16 eth_type, __be16 vlan_tci, - u32 mpls_label_count, bool log); + u32 mpls_label_count, bool log, + u32 depth); static int validate_and_copy_sample(struct net *net, const struct nlattr *attr, const struct sw_flow_key *key, struct sw_flow_actions **sfa, __be16 eth_type, __be16 vlan_tci, - u32 mpls_label_count, bool log, bool last) + u32 mpls_label_count, bool log, bool last, + u32 depth) { const struct nlattr *attrs[OVS_SAMPLE_ATTR_MAX + 1]; const struct nlattr *probability, *actions; @@ -2602,7 +2605,8 @@ static int validate_and_copy_sample(struct net *net, const struct nlattr *attr, return err; err = __ovs_nla_copy_actions(net, actions, key, sfa, - eth_type, vlan_tci, mpls_label_count, log); + eth_type, vlan_tci, mpls_label_count, log, + depth + 1); if (err) return err; @@ -2617,7 +2621,8 @@ static int validate_and_copy_dec_ttl(struct net *net, const struct sw_flow_key *key, struct sw_flow_actions **sfa, __be16 eth_type, __be16 vlan_tci, - u32 mpls_label_count, bool log) + u32 mpls_label_count, bool log, + u32 depth) { const struct nlattr *attrs[OVS_DEC_TTL_ATTR_MAX + 1]; int start, action_start, err, rem; @@ -2660,7 +2665,8 @@ static int validate_and_copy_dec_ttl(struct net *net, return action_start; err = __ovs_nla_copy_actions(net, actions, key, sfa, eth_type, - vlan_tci, mpls_label_count, log); + vlan_tci, mpls_label_count, log, + depth + 1); if (err) return err; @@ -2674,7 +2680,8 @@ static int validate_and_copy_clone(struct net *net, const struct sw_flow_key *key, struct sw_flow_actions **sfa, __be16 eth_type, __be16 vlan_tci, - u32 mpls_label_count, bool log, bool last) + u32 mpls_label_count, bool log, bool last, + u32 depth) { int start, err; u32 exec; @@ -2694,7 +2701,8 @@ static int validate_and_copy_clone(struct net *net, return err; err = __ovs_nla_copy_actions(net, attr, key, sfa, - eth_type, vlan_tci, mpls_label_count, log); + eth_type, vlan_tci, mpls_label_count, log, + depth + 1); if (err) return err; @@ -3063,7 +3071,7 @@ static int validate_and_copy_check_pkt_len(struct net *net, struct sw_flow_actions **sfa, __be16 eth_type, __be16 vlan_tci, u32 mpls_label_count, - bool log, bool last) + bool log, bool last, u32 depth) { const struct nlattr *acts_if_greater, *acts_if_lesser_eq; struct nlattr *a[OVS_CHECK_PKT_LEN_ATTR_MAX + 1]; @@ -3111,7 +3119,8 @@ static int validate_and_copy_check_pkt_len(struct net *net, return nested_acts_start; err = __ovs_nla_copy_actions(net, acts_if_lesser_eq, key, sfa, - eth_type, vlan_tci, mpls_label_count, log); + eth_type, vlan_tci, mpls_label_count, log, + depth + 1); if (err) return err; @@ -3124,7 +3133,8 @@ static int validate_and_copy_check_pkt_len(struct net *net, return nested_acts_start; err = __ovs_nla_copy_actions(net, acts_if_greater, key, sfa, - eth_type, vlan_tci, mpls_label_count, log); + eth_type, vlan_tci, mpls_label_count, log, + depth + 1); if (err) return err; @@ -3152,12 +3162,16 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, const struct sw_flow_key *key, struct sw_flow_actions **sfa, __be16 eth_type, __be16 vlan_tci, - u32 mpls_label_count, bool log) + u32 mpls_label_count, bool log, + u32 depth) { u8 mac_proto = ovs_key_mac_proto(key); const struct nlattr *a; int rem, err; + if (depth > OVS_COPY_ACTIONS_MAX_DEPTH) + return -EOVERFLOW; + nla_for_each_nested(a, attr, rem) { /* Expected argument lengths, (u32)-1 for variable length. */ static const u32 action_lens[OVS_ACTION_ATTR_MAX + 1] = { @@ -3355,7 +3369,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, err = validate_and_copy_sample(net, a, key, sfa, eth_type, vlan_tci, mpls_label_count, - log, last); + log, last, depth); if (err) return err; skip_copy = true; @@ -3426,7 +3440,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, err = validate_and_copy_clone(net, a, key, sfa, eth_type, vlan_tci, mpls_label_count, - log, last); + log, last, depth); if (err) return err; skip_copy = true; @@ -3440,7 +3454,8 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, eth_type, vlan_tci, mpls_label_count, - log, last); + log, last, + depth); if (err) return err; skip_copy = true; @@ -3450,7 +3465,8 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, case OVS_ACTION_ATTR_DEC_TTL: err = validate_and_copy_dec_ttl(net, a, key, sfa, eth_type, vlan_tci, - mpls_label_count, log); + mpls_label_count, log, + depth); if (err) return err; skip_copy = true; @@ -3495,7 +3511,8 @@ int ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, (*sfa)->orig_len = nla_len(attr); err = __ovs_nla_copy_actions(net, attr, key, sfa, key->eth.type, - key->eth.vlan.tci, mpls_label_count, log); + key->eth.vlan.tci, mpls_label_count, log, + 0); if (err) ovs_nla_free_flow_actions(*sfa); From bd128f62c365504e1268dc09fcccdfb1f091e93a Mon Sep 17 00:00:00 2001 From: Aaron Conole Date: Wed, 7 Feb 2024 08:24:16 -0500 Subject: [PATCH 2/2] selftests: openvswitch: Add validation for the recursion test Add a test case into the netlink checks that will show the number of nested action recursions won't exceed 16. Going to 17 on a small clone call isn't enough to exhaust the stack on (most) systems, so it should be safe to run even on systems that don't have the fix applied. Signed-off-by: Aaron Conole Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20240207132416.1488485-3-aconole@redhat.com Signed-off-by: Jakub Kicinski --- .../selftests/net/openvswitch/openvswitch.sh | 13 ++++ .../selftests/net/openvswitch/ovs-dpctl.py | 71 +++++++++++++++---- 2 files changed, 69 insertions(+), 15 deletions(-) diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh b/tools/testing/selftests/net/openvswitch/openvswitch.sh index f8499d4c87f3f..36e40256ab92a 100755 --- a/tools/testing/selftests/net/openvswitch/openvswitch.sh +++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh @@ -502,7 +502,20 @@ test_netlink_checks () { wc -l) == 2 ] || \ return 1 + info "Checking clone depth" ERR_MSG="Flow actions may not be safe on all matching packets" + PRE_TEST=$(dmesg | grep -c "${ERR_MSG}") + ovs_add_flow "test_netlink_checks" nv0 \ + 'in_port(1),eth(),eth_type(0x800),ipv4()' \ + 'clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(clone(drop)))))))))))))))))' \ + >/dev/null 2>&1 && return 1 + POST_TEST=$(dmesg | grep -c "${ERR_MSG}") + + if [ "$PRE_TEST" == "$POST_TEST" ]; then + info "failed - clone depth too large" + return 1 + fi + PRE_TEST=$(dmesg | grep -c "${ERR_MSG}") ovs_add_flow "test_netlink_checks" nv0 \ 'in_port(1),eth(),eth_type(0x0806),arp()' 'drop(0),2' \ diff --git a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py index b97e621face95..5e0e539a323d5 100644 --- a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py +++ b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py @@ -299,7 +299,7 @@ class ovsactions(nla): ("OVS_ACTION_ATTR_PUSH_NSH", "none"), ("OVS_ACTION_ATTR_POP_NSH", "flag"), ("OVS_ACTION_ATTR_METER", "none"), - ("OVS_ACTION_ATTR_CLONE", "none"), + ("OVS_ACTION_ATTR_CLONE", "recursive"), ("OVS_ACTION_ATTR_CHECK_PKT_LEN", "none"), ("OVS_ACTION_ATTR_ADD_MPLS", "none"), ("OVS_ACTION_ATTR_DEC_TTL", "none"), @@ -465,29 +465,42 @@ def dpstr(self, more=False): print_str += "pop_mpls" else: datum = self.get_attr(field[0]) - print_str += datum.dpstr(more) + if field[0] == "OVS_ACTION_ATTR_CLONE": + print_str += "clone(" + print_str += datum.dpstr(more) + print_str += ")" + else: + print_str += datum.dpstr(more) return print_str def parse(self, actstr): + totallen = len(actstr) while len(actstr) != 0: parsed = False + parencount = 0 if actstr.startswith("drop"): # If no reason is provided, the implicit drop is used (i.e no # action). If some reason is given, an explicit action is used. - actstr, reason = parse_extract_field( - actstr, - "drop(", - "([0-9]+)", - lambda x: int(x, 0), - False, - None, - ) + reason = None + if actstr.startswith("drop("): + parencount += 1 + + actstr, reason = parse_extract_field( + actstr, + "drop(", + "([0-9]+)", + lambda x: int(x, 0), + False, + None, + ) + if reason is not None: self["attrs"].append(["OVS_ACTION_ATTR_DROP", reason]) parsed = True else: - return + actstr = actstr[len("drop"): ] + return (totallen - len(actstr)) elif parse_starts_block(actstr, "^(\d+)", False, True): actstr, output = parse_extract_field( @@ -504,6 +517,7 @@ def parse(self, actstr): False, 0, ) + parencount += 1 self["attrs"].append(["OVS_ACTION_ATTR_RECIRC", recircid]) parsed = True @@ -516,12 +530,22 @@ def parse(self, actstr): for flat_act in parse_flat_map: if parse_starts_block(actstr, flat_act[0], False): - actstr += len(flat_act[0]) + actstr = actstr[len(flat_act[0]):] self["attrs"].append([flat_act[1]]) actstr = actstr[strspn(actstr, ", ") :] parsed = True - if parse_starts_block(actstr, "ct(", False): + if parse_starts_block(actstr, "clone(", False): + parencount += 1 + subacts = ovsactions() + actstr = actstr[len("clone("):] + parsedLen = subacts.parse(actstr) + lst = [] + self["attrs"].append(("OVS_ACTION_ATTR_CLONE", subacts)) + actstr = actstr[parsedLen:] + parsed = True + elif parse_starts_block(actstr, "ct(", False): + parencount += 1 actstr = actstr[len("ct(") :] ctact = ovsactions.ctact() @@ -553,6 +577,7 @@ def parse(self, actstr): natact = ovsactions.ctact.natattr() if actstr.startswith("("): + parencount += 1 t = None actstr = actstr[1:] if actstr.startswith("src"): @@ -607,15 +632,29 @@ def parse(self, actstr): actstr = actstr[strspn(actstr, ", ") :] ctact["attrs"].append(["OVS_CT_ATTR_NAT", natact]) - actstr = actstr[strspn(actstr, ",) ") :] + actstr = actstr[strspn(actstr, ", ") :] self["attrs"].append(["OVS_ACTION_ATTR_CT", ctact]) parsed = True - actstr = actstr[strspn(actstr, "), ") :] + actstr = actstr[strspn(actstr, ", ") :] + while parencount > 0: + parencount -= 1 + actstr = actstr[strspn(actstr, " "):] + if len(actstr) and actstr[0] != ")": + raise ValueError("Action str: '%s' unbalanced" % actstr) + actstr = actstr[1:] + + if len(actstr) and actstr[0] == ")": + return (totallen - len(actstr)) + + actstr = actstr[strspn(actstr, ", ") :] + if not parsed: raise ValueError("Action str: '%s' not supported" % actstr) + return (totallen - len(actstr)) + class ovskey(nla): nla_flags = NLA_F_NESTED @@ -2111,6 +2150,8 @@ def main(argv): ovsflow = OvsFlow() ndb = NDB() + sys.setrecursionlimit(100000) + if hasattr(args, "showdp"): found = False for iface in ndb.interfaces: