This is a note to let you know that I've just added the patch titled
net: do not use rcu in rtnl_dump_ifinfo()
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-do-not-use-rcu-in-rtnl_dump_ifinfo.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Wed Mar 11 11:44:33 CET 2015
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Fri, 27 Feb 2015 09:42:50 -0800
Subject: net: do not use rcu in rtnl_dump_ifinfo()
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit cac5e65e8a7ea074f2626d2eaa53aa308452dec4 ]
We did a failed attempt in the past to only use rcu in rtnl dump
operations (commit e67f88dd12f6 "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@xxxxxxxxxx>
Fixes: 0c7aecd4bde4b7302 ("netns: add rtnl cmd to add and get peer netns ids")
Cc: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
Reported-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/rtnetlink.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1274,7 +1274,6 @@ static int rtnl_dump_ifinfo(struct sk_bu
s_h = cb->args[0];
s_idx = cb->args[1];
- rcu_read_lock();
cb->seq = net->dev_base_seq;
/* A hack to preserve kernel<->userspace interface.
@@ -1296,7 +1295,7 @@ static int rtnl_dump_ifinfo(struct sk_bu
for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
idx = 0;
head = &net->dev_index_head[h];
- hlist_for_each_entry_rcu(dev, head, index_hlist) {
+ hlist_for_each_entry(dev, head, index_hlist) {
if (idx < s_idx)
goto cont;
err = rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK,
@@ -1318,7 +1317,6 @@ cont:
}
}
out:
- rcu_read_unlock();
cb->args[1] = idx;
cb->args[0] = h;
Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are
queue-3.19/net-pktgen-disable-xmit_clone-on-virtual-devices.patch
queue-3.19/net-do-not-use-rcu-in-rtnl_dump_ifinfo.patch
queue-3.19/flowcache-fix-kernel-panic-in-flow_cache_flush_task.patch
queue-3.19/tcp-make-sure-skb-is-not-shared-before-using-skb_get.patch
queue-3.19/sock-sock_dequeue_err_skb-needs-hard-irq-safety.patch
queue-3.19/macvtap-make-sure-neighbour-code-can-push-ethernet-header.patch
queue-3.19/ipv4-ip_check_defrag-should-correctly-check-return-value-of-skb_copy_bits.patch
--
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