linux-kernel - [RFC PATCH v2]nohz: protect smp_processor_id() in tick_nohz_task

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sun, 28 Apr 2013 11:25:58 +0800
From:	Li Zhong <zhong@...ux.vnet.ibm.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Subject: [RFC PATCH v2]nohz: protect smp_processor_id() in
 tick_nohz_task_switch()

I saw following error when testing the latest nohz code on Power:

[   85.295384] BUG: using smp_processor_id() in preemptible [00000000] code: rsyslogd/3493
[   85.295396] caller is .tick_nohz_task_switch+0x1c/0xb8
[   85.295402] Call Trace:
[   85.295408] [c0000001fababab0] [c000000000012dc4] .show_stack+0x110/0x25c (unreliable)
[   85.295420] [c0000001fababba0] [c0000000007c4b54] .dump_stack+0x20/0x30
[   85.295430] [c0000001fababc10] [c00000000044eb74] .debug_smp_processor_id+0xf4/0x124
[   85.295438] [c0000001fababca0] [c0000000000d7594] .tick_nohz_task_switch+0x1c/0xb8
[   85.295447] [c0000001fababd20] [c0000000000b9748] .finish_task_switch+0x13c/0x160
[   85.295455] [c0000001fababdb0] [c0000000000bbe50] .schedule_tail+0x50/0x124
[   85.295463] [c0000001fababe30] [c000000000009dc8] .ret_from_fork+0x4/0x54

The code below moves the test into local_irq_save/restore section to
avoid the above complaint.

Signed-off-by: Li Zhong <zhong@...ux.vnet.ibm.com>
---
 kernel/time/tick-sched.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index da53c8f..1c9f53b 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -251,14 +251,15 @@ void tick_nohz_task_switch(struct task_struct *tsk)
 {
 	unsigned long flags;
 
-	if (!tick_nohz_full_cpu(smp_processor_id()))
-		return;
-
 	local_irq_save(flags);
 
+	if (!tick_nohz_full_cpu(smp_processor_id()))
+		goto out;
+
 	if (tick_nohz_tick_stopped() && !can_stop_full_tick())
 		tick_nohz_full_kick();
 
+out:
 	local_irq_restore(flags);
 }
 
-- 
1.7.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/