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net/sched: sch_fq: fix integer overflow of "credit"

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if sch_fq is configured with "initial quantum" having values greater than
INT_MAX, the first assignment of "credit" does signed integer overflow to
a very negative value.
In this situation, the syzkaller script provided by Cristoph triggers the
CPU soft-lockup warning even with few sockets. It's not an infinite loop,
but "credit" wasn't probably meant to be minus 2Gb for each new flow.
Capping "initial quantum" to INT_MAX proved to fix the issue.

v2: validation of "initial quantum" is done in fq_policy, instead of open
    coding in fq_change() _ suggested by Jakub Kicinski

Reported-by: Christoph Paasch <cpaasch@apple.com>
Link: https://github.com/multipath-tcp/mptcp_net-next/issues/377
Fixes: afe4fd0624 ("pkt_sched: fq: Fair Queue packet scheduler")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/7b3a3c7e36d03068707a021760a194a8eb5ad41a.1682002300.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Davide Caratti 2023-04-20 16:59:46 +02:00 committed by Jakub Kicinski
parent 63cfd21003
commit 7041101ff6
2 changed files with 27 additions and 1 deletions
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6
net/sched/sch_fq.c
View File

@ -779,13 +779,17 @@ static int fq_resize(struct Qdisc *sch, u32 log)
return 0;
}
static struct netlink_range_validation iq_range = {
.max = INT_MAX,
};
static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = {
[TCA_FQ_UNSPEC] = { .strict_start_type = TCA_FQ_TIMER_SLACK },
[TCA_FQ_PLIMIT] = { .type = NLA_U32 },
[TCA_FQ_FLOW_PLIMIT] = { .type = NLA_U32 },
[TCA_FQ_QUANTUM] = { .type = NLA_U32 },
[TCA_FQ_INITIAL_QUANTUM] = { .type = NLA_U32 },
[TCA_FQ_INITIAL_QUANTUM] = NLA_POLICY_FULL_RANGE(NLA_U32, &iq_range),
[TCA_FQ_RATE_ENABLE] = { .type = NLA_U32 },
[TCA_FQ_FLOW_DEFAULT_RATE] = { .type = NLA_U32 },
[TCA_FQ_FLOW_MAX_RATE] = { .type = NLA_U32 },

22
tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json
View File

@ -114,6 +114,28 @@
"$IP link del dev $DUMMY type dummy"
]
},
{
"id": "10f7",
"name": "Create FQ with invalid initial_quantum setting",
"category": [
"qdisc",
"fq"
],
"plugins": {
"requires": "nsPlugin"
},
"setup": [
"$IP link add dev $DUMMY type dummy || /bin/true"
],
"cmdUnderTest": "$TC qdisc add dev $DUMMY handle 1: root fq initial_quantum 0x80000000",
"expExitCode": "2",
"verifyCmd": "$TC qdisc show dev $DUMMY",
"matchPattern": "qdisc fq 1: root.*initial_quantum 2048Mb",
"matchCount": "0",
"teardown": [
"$IP link del dev $DUMMY type dummy"
]
},
{
"id": "9398",
"name": "Create FQ with maxrate setting",