From cc9f4daa638e660f7a910b8094122561470ac331 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Wed, 22 Jul 2015 12:23:20 +0300 Subject: [PATCH] cgroup: net_cls: fix false-positive "suspicious RCU usage" In dev_queue_xmit() net_cls protected with rcu-bh. [ 270.730026] =============================== [ 270.730029] [ INFO: suspicious RCU usage. ] [ 270.730033] 4.2.0-rc3+ #2 Not tainted [ 270.730036] ------------------------------- [ 270.730040] include/linux/cgroup.h:353 suspicious rcu_dereference_check() usage! [ 270.730041] other info that might help us debug this: [ 270.730043] rcu_scheduler_active = 1, debug_locks = 1 [ 270.730045] 2 locks held by dhclient/748: [ 270.730046] #0: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x50/0x960 [ 270.730085] #1: (&qdisc_tx_lock){+.....}, at: [] __dev_queue_xmit+0x240/0x960 [ 270.730090] stack backtrace: [ 270.730096] CPU: 0 PID: 748 Comm: dhclient Not tainted 4.2.0-rc3+ #2 [ 270.730098] Hardware name: OpenStack Foundation OpenStack Nova, BIOS Bochs 01/01/2011 [ 270.730100] 0000000000000001 ffff8800bafeba58 ffffffff817ad487 0000000000000007 [ 270.730103] ffff880232a0a780 ffff8800bafeba88 ffffffff810ca4f2 ffff88022fb23e00 [ 270.730105] ffff880232a0a780 ffff8800bafebb68 ffff8800bafebb68 ffff8800bafebaa8 [ 270.730108] Call Trace: [ 270.730121] [] dump_stack+0x4c/0x65 [ 270.730148] [] lockdep_rcu_suspicious+0xe2/0x120 [ 270.730153] [] task_cls_state+0x92/0xa0 [ 270.730158] [] cls_cgroup_classify+0x4f/0x120 [cls_cgroup] [ 270.730164] [] tc_classify_compat+0x74/0xc0 [ 270.730166] [] tc_classify+0x33/0x90 [ 270.730170] [] htb_enqueue+0xaa/0x4a0 [sch_htb] [ 270.730172] [] __dev_queue_xmit+0x306/0x960 [ 270.730174] [] ? __dev_queue_xmit+0x50/0x960 [ 270.730176] [] dev_queue_xmit_sk+0x13/0x20 [ 270.730185] [] dev_queue_xmit+0x10/0x20 [ 270.730187] [] packet_snd.isra.62+0x54c/0x760 [ 270.730190] [] packet_sendmsg+0x2f5/0x3f0 [ 270.730203] [] ? sock_def_readable+0x5/0x190 [ 270.730210] [] ? _raw_spin_unlock+0x2b/0x40 [ 270.730216] [] ? unix_dgram_sendmsg+0x5cc/0x640 [ 270.730219] [] sock_sendmsg+0x47/0x50 [ 270.730221] [] sock_write_iter+0x7f/0xd0 [ 270.730232] [] __vfs_write+0xa7/0xf0 [ 270.730234] [] vfs_write+0xb8/0x190 [ 270.730236] [] SyS_write+0x52/0xb0 [ 270.730239] [] entry_SYSCALL_64_fastpath+0x12/0x76 Signed-off-by: Konstantin Khlebnikov Signed-off-by: David S. Miller --- net/core/netclassid_cgroup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c index 1f2a126f4ffa..6441f47b1a8f 100644 --- a/net/core/netclassid_cgroup.c +++ b/net/core/netclassid_cgroup.c @@ -23,7 +23,8 @@ static inline struct cgroup_cls_state *css_cls_state(struct cgroup_subsys_state struct cgroup_cls_state *task_cls_state(struct task_struct *p) { - return css_cls_state(task_css(p, net_cls_cgrp_id)); + return css_cls_state(task_css_check(p, net_cls_cgrp_id, + rcu_read_lock_bh_held())); } EXPORT_SYMBOL_GPL(task_cls_state); -- 2.30.2