From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit c7c5e6ff533fe1f9afef7d2fa46678987a1335a7 ]
syzbot found that forcing a big quantum attribute would crash hosts fast,
essentially using this:
tc qd replace dev eth0 root fq_codel quantum 4294967295
This is because fq_codel_dequeue() would have to loop
~2^31 times in :
if (flow->deficit <= 0) {
flow->deficit += q->quantum;
list_move_tail(&flow->flowchain, &q->old_flows);
goto begin;
}
SFQ max quantum is 2^19 (half a megabyte)
Lets adopt a max quantum of one megabyte for FQ_CODEL.
Fixes: 4b549a2ef4be ("fq_codel: Fair Queue Codel AQM")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/uapi/linux/pkt_sched.h | 2 ++
net/sched/sch_fq_codel.c | 12 ++++++++++--
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index edbbf4bfdd9e..4a245d7a5c8d 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -807,6 +807,8 @@ struct tc_codel_xstats {
/* FQ_CODEL */
+#define FQ_CODEL_QUANTUM_MAX (1 << 20)
+
enum {
TCA_FQ_CODEL_UNSPEC,
TCA_FQ_CODEL_TARGET,
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index 76d72c3f52ed..86fb2f953bd5 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -370,6 +370,7 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
{
struct fq_codel_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
+ u32 quantum = 0;
int err;
if (!opt)
@@ -387,6 +388,13 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
q->flows_cnt > 65536)
return -EINVAL;
}
+ if (tb[TCA_FQ_CODEL_QUANTUM]) {
+ quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
+ if (quantum > FQ_CODEL_QUANTUM_MAX) {
+ NL_SET_ERR_MSG(extack, "Invalid quantum");
+ return -EINVAL;
+ }
+ }
sch_tree_lock(sch);
if (tb[TCA_FQ_CODEL_TARGET]) {
@@ -413,8 +421,8 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
if (tb[TCA_FQ_CODEL_ECN])
q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]);
- if (tb[TCA_FQ_CODEL_QUANTUM])
- q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
+ if (quantum)
+ q->quantum = quantum;
if (tb[TCA_FQ_CODEL_DROP_BATCH_SIZE])
q->drop_batch_size = max(1U, nla_get_u32(tb[TCA_FQ_CODEL_DROP_BATCH_SIZE]));
--
2.30.2
