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| author | Eric Dumazet <edumazet@google.com> | 2021-09-03 15:03:43 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-09-04 10:49:46 +0100 |
| commit | c7c5e6ff533fe1f9afef7d2fa46678987a1335a7 (patch) | |
| tree | 73d9af6b6cc1fc846633747ce81c900a46e27960 /net | |
| parent | 10905b4a68cc58863e04d5ea5864323cb9341f9b (diff) | |
| download | lwn-c7c5e6ff533fe1f9afef7d2fa46678987a1335a7.tar.gz lwn-c7c5e6ff533fe1f9afef7d2fa46678987a1335a7.zip | |
fq_codel: reject silly quantum parameters
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@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sched/sch_fq_codel.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c index c4afdd026f51..bb0cd6d3d2c2 100644 --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -369,6 +369,7 @@ 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) @@ -386,6 +387,13 @@ 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]) { @@ -412,8 +420,8 @@ 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])); |