tcf_gate_get_fill_size returns only the TCA_GATE_PARMS size, but
tcf_gate_dump also emits three 64-bit timestamps, the clock id, flags,
priority and the variable-length TCA_GATE_ENTRY_LIST nest. The per-entry
nest is unbounded: parse_gate_list places no cap on the number of
sched-entries, so a gate with many entries can push the real dump well
past the skb that tca_get_fill allocates from this size.
RTM_NEWACTION then fails the add-notify with -EINVAL while the action is
already committed to the IDR, and a subsequent RTM_GETACTION on the
installed gate also returns -EINVAL because its dump no longer fits.
Fix this by accounting for the missing fields in tcf_gate_get_fill_size
along with all elements in the entries list.
Note that sizing the reply from the action lets an oversized gate
install cleanly for the first time: with the input unbounded by
parse_gate_list, the sized skb can now grow well above
NLMSG_GOODSIZE per netlink request (a transient GFP_KERNEL allocation
reachable only with namespace-local CAP_NET_ADMIN). Overload from a
malicious netns admin is hardening material, not net, per the
discussion at
https://lore.kernel.org/netdev/20260914191108.55a1a4f1@kernel.org/;
a follow-up patch for net-next will cap the sched-entry count.
Fixes: 4e76e75d6a ("net sched actions: calculate add/delete event message size")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260824153903.4143642-1-victor@mojatatu.com
Tested-by: hybris <hybris@mojatatu.ai>
Co-developed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Link: https://patch.msgid.link/QDISC-3BLH.v1.20260914203033@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
cfa165cbfb