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Eric Dumazet cac5e65e8a net: do not use rcu in rtnl_dump_ifinfo() 
We did a failed attempt in the past to only use rcu in rtnl dump
operations (commit e67f88dd12 "net: dont hold rtnl mutex during
netlink dump callbacks")

Now that dumps are holding RTNL anyway, there is no need to also
use rcu locking, as it forbids any scheduling ability, like
GFP_KERNEL allocations that controlling path should use instead
of GFP_ATOMIC whenever possible.

This should fix following splat Cong Wang reported :

 [ INFO: suspicious RCU usage. ]
 3.19.0+ #805 Tainted: G        W

 include/linux/rcupdate.h:538 Illegal context switch in RCU read-side critical section!

 other info that might help us debug this:

 rcu_scheduler_active = 1, debug_locks = 0
 2 locks held by ip/771:
  #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff8182b8f4>] netlink_dump+0x21/0x26c
  #1:  (rcu_read_lock){......}, at: [<ffffffff817d785b>] rcu_read_lock+0x0/0x6e

 stack backtrace:
 CPU: 3 PID: 771 Comm: ip Tainted: G        W       3.19.0+ #805
 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
  0000000000000001 ffff8800d51e7718 ffffffff81a27457 0000000029e729e6
  ffff8800d6108000 ffff8800d51e7748 ffffffff810b539b ffffffff820013dd
  00000000000001c8 0000000000000000 ffff8800d7448088 ffff8800d51e7758
 Call Trace:
  [<ffffffff81a27457>] dump_stack+0x4c/0x65
  [<ffffffff810b539b>] lockdep_rcu_suspicious+0x107/0x110
  [<ffffffff8109796f>] rcu_preempt_sleep_check+0x45/0x47
  [<ffffffff8109e457>] ___might_sleep+0x1d/0x1cb
  [<ffffffff8109e67d>] __might_sleep+0x78/0x80
  [<ffffffff814b9b1f>] idr_alloc+0x45/0xd1
  [<ffffffff810cb7ab>] ? rcu_read_lock_held+0x3b/0x3d
  [<ffffffff814b9f9d>] ? idr_for_each+0x53/0x101
  [<ffffffff817c1383>] alloc_netid+0x61/0x69
  [<ffffffff817c14c3>] __peernet2id+0x79/0x8d
  [<ffffffff817c1ab7>] peernet2id+0x13/0x1f
  [<ffffffff817d8673>] rtnl_fill_ifinfo+0xa8d/0xc20
  [<ffffffff810b17d9>] ? __lock_is_held+0x39/0x52
  [<ffffffff817d894f>] rtnl_dump_ifinfo+0x149/0x213
  [<ffffffff8182b9c2>] netlink_dump+0xef/0x26c
  [<ffffffff8182bcba>] netlink_recvmsg+0x17b/0x2c5
  [<ffffffff817b0adc>] __sock_recvmsg+0x4e/0x59
  [<ffffffff817b1b40>] sock_recvmsg+0x3f/0x51
  [<ffffffff817b1f9a>] ___sys_recvmsg+0xf6/0x1d9
  [<ffffffff8115dc67>] ? handle_pte_fault+0x6e1/0xd3d
  [<ffffffff8100a3a0>] ? native_sched_clock+0x35/0x37
  [<ffffffff8109f45b>] ? sched_clock_local+0x12/0x72
  [<ffffffff8109f6ac>] ? sched_clock_cpu+0x9e/0xb7
  [<ffffffff810cb7ab>] ? rcu_read_lock_held+0x3b/0x3d
  [<ffffffff811abde8>] ? __fcheck_files+0x4c/0x58
  [<ffffffff811ac556>] ? __fget_light+0x2d/0x52
  [<ffffffff817b376f>] __sys_recvmsg+0x42/0x60
  [<ffffffff817b379f>] SyS_recvmsg+0x12/0x1c

Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 0c7aecd4bd ("netns: add rtnl cmd to add and get peer netns ids")
Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reported-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2015-03-01 00:07:00 -05:00
..
Makefile net: bury net/core/iovec.c - nothing in there is used anymore 2015-02-04 01:34:15 -05:00
datagram.c skb_copy_datagram_iovec() can die 2014-12-09 16:29:11 -05:00
dev.c net: reject creation of netdev names with colons 2015-02-21 21:45:25 -05:00
dev_addr_lists.c net: fix spelling for synchronized 2014-11-18 15:26:32 -05:00
dev_ioctl.c dev_ioctl: use sizeof(x) instead of sizeof x 2014-11-18 15:27:32 -05:00
drop_monitor.c net: Replace get_cpu_var through this_cpu_ptr 2014-08-26 13:45:47 -04:00
dst.c dst: no need to take reference on DST_NOCACHE dsts 2014-12-09 16:08:17 -05:00
ethtool.c ethtool: Add hw-switch-offload to netdev_features_strings. 2015-02-20 16:36:43 -05:00
fib_rules.c netlink: make nlmsg_end() and genlmsg_end() void 2015-01-18 01:03:45 -05:00
filter.c net: spelling fixes 2015-02-14 20:36:08 -08:00
flow.c flowcache: Fix kernel panic in flow_cache_flush_task 2015-02-05 14:38:53 -08:00
flow_dissector.c xps: fix xps for stacked devices 2015-02-04 13:02:54 -08:00
gen_estimator.c net: sched: make bstats per cpu and estimator RCU safe 2014-09-30 01:02:26 -04:00
gen_stats.c gen_stats.c: Duplicate xstats buffer for later use 2015-02-19 15:45:53 -05:00
link_watch.c net/core: include linux/types.h instead of asm/types.h 2014-11-18 15:26:32 -05:00
neighbour.c netlink: Fix bugs in nlmsg_end() conversions. 2015-01-18 23:36:08 -05:00
net-procfs.c rps: selective flow shedding during softnet overflow 2013-05-20 13:48:04 -07:00
net-sysfs.c net: use %*pb[l] to print bitmaps including cpumasks and nodemasks 2015-02-13 21:21:38 -08:00
net-sysfs.h net: netdev_kobject_init: annotate with __init 2014-01-05 20:27:54 -05:00
net-traces.c net: Add export.h for EXPORT_SYMBOL/THIS_MODULE to non-modules 2011-10-31 19:30:30 -04:00
net_namespace.c Last round of updates for net-next: 2015-02-04 14:57:45 -08:00
netclassid_cgroup.c cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes 2014-07-15 11:05:09 -04:00
netevent.c net: Add export.h for EXPORT_SYMBOL/THIS_MODULE to non-modules 2011-10-31 19:30:30 -04:00
netpoll.c net: rename vlan_tx_* helpers since "tx" is misleading there 2015-01-13 17:51:08 -05:00
netprio_cgroup.c cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes 2014-07-15 11:05:09 -04:00
pktgen.c net: pktgen: disable xmit_clone on virtual devices 2015-02-22 22:43:20 -05:00
ptp_classifier.c net: filter: split 'struct sk_filter' into socket and bpf parts 2014-08-02 15:03:58 -07:00
request_sock.c inet: reduce TLB pressure for listeners 2014-06-25 16:37:24 -07:00
rtnetlink.c net: do not use rcu in rtnl_dump_ifinfo() 2015-03-01 00:07:00 -05:00
scm.c net: introduce helper macro for_each_cmsghdr 2014-12-10 22:41:55 -05:00
secure_seq.c net: use ktime_get_ns() and ktime_get_real_ns() helpers 2014-08-22 19:57:23 -07:00
skbuff.c sock: sock_dequeue_err_skb() needs hard irq safety 2015-02-20 15:52:21 -05:00
sock.c net-timestamp: no-payload only sysctl 2015-02-02 18:46:51 -08:00
sock_diag.c net: filter: split 'struct sk_filter' into socket and bpf parts 2014-08-02 15:03:58 -07:00
stream.c net: replace macros net_random and net_srandom with direct calls to prandom 2014-01-14 15:15:25 -08:00
sysctl_net_core.c net: use %*pb[l] to print bitmaps including cpumasks and nodemasks 2015-02-13 21:21:38 -08:00
timestamping.c net-timestamp: Make the clone operation stand-alone from phy timestamping 2014-09-05 17:43:45 -07:00
tso.c net: tso: fix unaligned access to crafted TCP header in helper API 2014-10-22 12:52:55 -04:00
utils.c net: Convert LIMIT_NETDEBUG to net_dbg_ratelimited 2014-11-11 14:10:31 -05:00