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Several tc actions - act_police, act_bpf, act_pedit, act_ife, act_sample,
act_ct, act_ctinfo and act_tunnel_key among them - provide no
get_fill_size() callback, so tcf_action_fill_size() falls back to
tcf_action_shared_attrs_size() which does not account for the
action-specific netlink attributes emitted inside TCA_ACT_OPTIONS by
their dump functions.
When an RTM_NEWACTION request with NLM_F_ECHO (or an RTNLGRP_TC
listener) creates several actions, tcf_add_notify_msg() allocates the
echo skb from this underestimated size. When this happens, the act_api
code fails to add all of the fields to the netlink message and, thus,
fails to send it. Issue is that, when that happens, this failure doesn't
stop the action instances from being added. So any user watching these
events will be under the false impression that no actions were created at
all.
For example, act_pedit overruns with 32 actions of four munge keys each,
act_police with 32 policers once the optional rate/peakrate/result/avrate
attributes are present.
To fix this, add the missing get_fill_size callbacks returning the
worst-case size of each action's dump attributes, following the pattern
used by act_gact/act_skbedit/act_vlan. Also widen the TCA_GACT_TM
accounting in tcf_action_shared_attrs_size() to nla_total_size_64bit(),
since actions dump their tcf_t with nla_put_64bit(), which may be
preceded by an NLA_PAD attribute.
Note: We only provided fixes for the actions we reproduced this bug with
as of today. We can send a separate hardening patch for the remaining
actions to net-next later. The other pre-existing issues, pointed out by
Clashiko [1], will be fixed in upcoming patches.
[1] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260810164357.1653956-1-victor%40mojatatu.com
Fixes: 4e76e75d6a ("net sched actions: calculate add/delete event message size")
Reported-by: Vega <vega@nebusec.ai>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260816201327.2435335-1-victor@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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