From 368ffd9adc7a01234c0c68ffd72cc76840f20134 Mon Sep 17 00:00:00 2001 From: Qinglang Miao Date: Thu, 19 Nov 2020 15:08:39 +0800 Subject: [PATCH] ipmi: msghandler: Suppress suspicious RCU usage warning while running ipmi, ipmi_smi_watcher_register() caused a suspicious RCU usage warning. ----- ============================= WARNING: suspicious RCU usage 5.10.0-rc3+ #1 Not tainted ----------------------------- drivers/char/ipmi/ipmi_msghandler.c:750 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by syz-executor.0/4254: stack backtrace: CPU: 0 PID: 4254 Comm: syz-executor.0 Not tainted 5.10.0-rc3+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/ 01/2014 Call Trace: dump_stack+0x19d/0x200 ipmi_smi_watcher_register+0x2d3/0x340 [ipmi_msghandler] acpi_ipmi_init+0xb1/0x1000 [acpi_ipmi] do_one_initcall+0x149/0x7e0 do_init_module+0x1ef/0x700 load_module+0x3467/0x4140 __do_sys_finit_module+0x10d/0x1a0 do_syscall_64+0x34/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x468ded ----- It is safe because smi_watchers_mutex is locked and srcu_read_lock has been used, so simply pass lockdep_is_held() to the list_for_each_entry_rcu() to suppress this warning. Reported-by: Hulk Robot Signed-off-by: Qinglang Miao Message-Id: <20201119070839.381-1-miaoqinglang@huawei.com> Signed-off-by: Corey Minyard --- drivers/char/ipmi/ipmi_msghandler.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index 8774a3b8ff95..c44ad18464f1 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -747,7 +747,8 @@ int ipmi_smi_watcher_register(struct ipmi_smi_watcher *watcher) list_add(&watcher->link, &smi_watchers); index = srcu_read_lock(&ipmi_interfaces_srcu); - list_for_each_entry_rcu(intf, &ipmi_interfaces, link) { + list_for_each_entry_rcu(intf, &ipmi_interfaces, link, + lockdep_is_held(&smi_watchers_mutex)) { int intf_num = READ_ONCE(intf->intf_num); if (intf_num == -1)