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>
Test 983b: Create FQ with default setting
Test 38a1: Create FQ with limit packet setting
Test 0a18: Create FQ with flow_limit setting
Test 2390: Create FQ with quantum setting
Test 845b: Create FQ with initial_quantum setting
Test 9398: Create FQ with maxrate setting
Test 342c: Create FQ with nopacing setting
Test 6391: Create FQ with refill_delay setting
Test 238b: Create FQ with low_rate_threshold setting
Test 7582: Create FQ with orphan_mask setting
Test 4894: Create FQ with timer_slack setting
Test 324c: Create FQ with ce_threshold setting
Test 424a: Create FQ with horizon time setting
Test 89e1: Create FQ with horizon_cap setting
Test 32e1: Delete FQ with valid handle
Test 49b0: Replace FQ with limit setting
Test 9478: Change FQ with limit setting
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
