diff options
| author | Victor Nogueira <victor@mojatatu.com> | 2026-08-24 12:39:01 -0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-08-28 15:56:06 -0700 |
| commit | e9ca46ebc3262b498626c4095826b8fa034bbf21 (patch) | |
| tree | 859d11104876fd60473a0de397cb873234934dd5 | |
| parent | 13eb543cebef6d6c3ec42e31afe3856f51b7126b (diff) | |
net/sched: act_api: size the RTM_GETACTION reply from the actions
tca_action_gd() already walks every requested action and accumulates
attr_size += tcf_action_fill_size(act), then wraps the result in
tcf_action_full_attrs_size(). For RTM_DELACTION that value is handed to
tcf_del_notify_msg(), which allocates max(attr_size, NLMSG_GOODSIZE). For
RTM_GETACTION it is silently discarded and tcf_get_notify() allocates a
fixed NLMSG_GOODSIZE skb instead.
Any action whose dump exceeds that fixed budget therefore cannot be read
back. For example, act_pedit overruns the budget with 32 actions of four
munge keys each, act_police with 32 policers once the optional
rate/peakrate/result/avrate attributes are present
Fix this by passing attr_size through and allocate the reply the way the
add and delete paths do.
Note on exposure: RTM_GETACTION is the only one of the three action
commands that is not capability checked - tc_ctl_action() requires
CAP_NET_ADMIN for RTM_NEWACTION and RTM_DELACTION only - so this turns a
fixed NLMSG_GOODSIZE reply into a user sized allocation on an
unprivileged path. It is bounded by TCA_ACT_MAX_PRIO actions per
request, and tca_action_gd() does not reject duplicate indices, so a
single large action can be requested 32 times; an act_bpf program near
BPF_MAXINSNS is about 32KB of dump, or roughly 1MB for one request.
Creating such an action still requires CAP_NET_ADMIN, and the add and
delete paths have sized their skbs this way since the Fixes commit.
Should this ever need bounding, GFP_KERNEL_ACCOUNT would charge the
reply to the caller's memcg.
Fixes: 4e76e75d6aba ("net sched actions: calculate add/delete event message size")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260810164357.1653956-1-victor%40mojatatu.com
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Link: https://patch.msgid.link/20260824153903.4143642-3-victor@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/sched/act_api.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/net/sched/act_api.c b/net/sched/act_api.c index 766162b0b810..20b6501fd33b 100644 --- a/net/sched/act_api.c +++ b/net/sched/act_api.c @@ -1697,12 +1697,12 @@ out_nlmsg_trim: static int tcf_get_notify(struct net *net, u32 portid, struct nlmsghdr *n, - struct tc_action *actions[], int event, + struct tc_action *actions[], size_t attr_size, int event, struct netlink_ext_ack *extack) { struct sk_buff *skb; - skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL); + skb = alloc_skb(max(attr_size, NLMSG_GOODSIZE), GFP_KERNEL); if (!skb) return -ENOBUFS; if (tca_get_fill(skb, actions, portid, n->nlmsg_seq, 0, event, @@ -2053,7 +2053,8 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct nlmsghdr *n, attr_size = tcf_action_full_attrs_size(attr_size); if (event == RTM_GETACTION) - ret = tcf_get_notify(net, portid, n, actions, event, extack); + ret = tcf_get_notify(net, portid, n, actions, attr_size, event, + extack); else { /* delete */ ret = tcf_del_notify(net, n, actions, portid, attr_size, extack); if (ret) |