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| author | Stephen Hemminger <stephen@networkplumber.org> | 2024-09-01 11:16:07 -0700 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2024-09-03 11:44:23 -0700 |
| commit | 3b3a2a9c6349e25a025d2330f479bc33a6ccb54a (patch) | |
| tree | 1472a89d1a04fe7e1daa0e866bff50fc572a4cb7 /net | |
| parent | bab8eb0dd4cb995caa4a0529d5655531c2ec5e8e (diff) | |
| download | lwn-3b3a2a9c6349e25a025d2330f479bc33a6ccb54a.tar.gz lwn-3b3a2a9c6349e25a025d2330f479bc33a6ccb54a.zip | |
sch/netem: fix use after free in netem_dequeue
If netem_dequeue() enqueues packet to inner qdisc and that qdisc
returns __NET_XMIT_STOLEN. The packet is dropped but
qdisc_tree_reduce_backlog() is not called to update the parent's
q.qlen, leading to the similar use-after-free as Commit
e04991a48dbaf382 ("netem: fix return value if duplicate enqueue
fails")
Commands to trigger KASAN UaF:
ip link add type dummy
ip link set lo up
ip link set dummy0 up
tc qdisc add dev lo parent root handle 1: drr
tc filter add dev lo parent 1: basic classid 1:1
tc class add dev lo classid 1:1 drr
tc qdisc add dev lo parent 1:1 handle 2: netem
tc qdisc add dev lo parent 2: handle 3: drr
tc filter add dev lo parent 3: basic classid 3:1 action mirred egress
redirect dev dummy0
tc class add dev lo classid 3:1 drr
ping -c1 -W0.01 localhost # Trigger bug
tc class del dev lo classid 1:1
tc class add dev lo classid 1:1 drr
ping -c1 -W0.01 localhost # UaF
Fixes: 50612537e9ab ("netem: fix classful handling")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Link: https://patch.msgid.link/20240901182438.4992-1-stephen@networkplumber.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sched/sch_netem.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 0f8d581438c3..39382ee1e331 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -742,11 +742,10 @@ deliver: err = qdisc_enqueue(skb, q->qdisc, &to_free); kfree_skb_list(to_free); - if (err != NET_XMIT_SUCCESS && - net_xmit_drop_count(err)) { - qdisc_qstats_drop(sch); - qdisc_tree_reduce_backlog(sch, 1, - pkt_len); + if (err != NET_XMIT_SUCCESS) { + if (net_xmit_drop_count(err)) + qdisc_qstats_drop(sch); + qdisc_tree_reduce_backlog(sch, 1, pkt_len); } goto tfifo_dequeue; } |