On Thu, Jul 27, 2023 at 08:41:49PM +0000, Shaoying Xu wrote:
[ Upstream commit 3e337087c3b5805fe0b8a46ba622a962880b5d64 ]
Lion says:
In the QFQ scheduler a similar issue to CVE-2023-31436 persists.
Consider the following code in net/sched/sch_qfq.c:
static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) { unsigned int len = qdisc_pkt_len(skb), gso_segs;
// ... if (unlikely(cl->agg->lmax < len)) { pr_debug("qfq: increasing maxpkt from %u to %u for class %u", cl->agg->lmax, len, cl->common.classid); err = qfq_change_agg(sch, cl, cl->agg->class_weight, len); if (err) { cl->qstats.drops++; return qdisc_drop(skb, sch, to_free); } // ... }Similarly to CVE-2023-31436, "lmax" is increased without any bounds checks according to the packet length "len". Usually this would not impose a problem because packet sizes are naturally limited.
This is however not the actual packet length, rather the "qdisc_pkt_len(skb)" which might apply size transformations according to "struct qdisc_size_table" as created by "qdisc_get_stab()" in net/sched/sch_api.c if the TCA_STAB option was set when modifying the qdisc.
A user may choose virtually any size using such a table.
As a result the same issue as in CVE-2023-31436 can occur, allowing heap out-of-bounds read / writes in the kmalloc-8192 cache.
We can create the issue with the following commands:
tc qdisc add dev $DEV root handle 1: stab mtu 2048 tsize 512 mpu 0 \ overhead 999999999 linklayer ethernet qfq tc class add dev $DEV parent 1: classid 1:1 htb rate 6mbit burst 15k tc filter add dev $DEV parent 1: matchall classid 1:1 ping -I $DEV 1.1.1.2
This is caused by incorrectly assuming that qdisc_pkt_len() returns a length within the QFQ_MIN_LMAX < len < QFQ_MAX_LMAX.
Fixes: 462dbc9101ac ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost") Reported-by: Lion nnamrec@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: Pedro Tammela pctammela@mojatatu.com Reviewed-by: Simon Horman simon.horman@corigine.com Signed-off-by: Paolo Abeni pabeni@redhat.com [Backport patch for stable kernels 4.14 and 5.4. Since QFQ_MAX_LMAX is not defined, replace it with 1UL << QFQ_MTU_SHIFT.] Cc: stable@vger.kernel.org # 4.14, 5.4 Signed-off-by: Shaoying Xu shaoyi@amazon.com
net/sched/sch_qfq.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
Now queued up, thanks.
greg k-h