From: Davide Caratti <dcaratti@redhat.com>
Date: Thu, 20 Apr 2023 16:59:46 +0200
Subject: [PATCH] net/sched: sch_fq: fix integer overflow of "credit"
References: bsc#1012628
Patch-mainline: 6.3.2
Git-commit: 7041101ff6c3073fd8f2e99920f535b111c929cb

[ Upstream commit 7041101ff6c3073fd8f2e99920f535b111c929cb ]

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: afe4fd062416 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 net/sched/sch_fq.c                            |  6 ++++-
 .../tc-testing/tc-tests/qdiscs/fq.json        | 22 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 48d14fb9..f59a2cb2 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -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 },
diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json
index 8acb904d..3593fb8f 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json
@@ -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",
-- 
2.35.3