Commit 7041101f authored by Davide Caratti's avatar Davide Caratti Committed by Jakub Kicinski
Browse files

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



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: default avatarChristoph Paasch <cpaasch@apple.com>
Link: https://github.com/multipath-tcp/mptcp_net-next/issues/377


Fixes: afe4fd06 ("pkt_sched: fq: Fair Queue packet scheduler")
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/7b3a3c7e36d03068707a021760a194a8eb5ad41a.1682002300.git.dcaratti@redhat.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 63cfd210

net/sched/sch_fq.c

+5 −1
Original line number Diff line number Diff line
@@ -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 },

tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json

+22 −0
Original line number Diff line number Diff line
@@ -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",