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Subject[PATCH 4.15 08/23] ipv6: addrconf: break critical section in addrconf_verify_rtnl()
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>


[ Upstream commit e64e469b9a2c22d41b3dd7172118760cec22d473 ]

Heiner reported a lockdep splat [1]

This is caused by attempting GFP_KERNEL allocation while RCU lock is
held and BH blocked.

We believe that addrconf_verify_rtnl() could run for a long period,
so instead of using GFP_ATOMIC here as Ido suggested, we should break
the critical section and restart it after the allocation.

[1]
[86220.125562] =============================
[86220.125586] WARNING: suspicious RCU usage
[86220.125612] 4.15.0-rc7-next-20180110+ #7 Not tainted
[86220.125641] -----------------------------
[86220.125666] kernel/sched/core.c:6026 Illegal context switch in RCU-bh read-side critical section!
[86220.125711]
other info that might help us debug this:

[86220.125755]
rcu_scheduler_active = 2, debug_locks = 1
[86220.125792] 4 locks held by kworker/0:2/1003:
[86220.125817] #0: ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000da8e9b73>] process_one_work+0x1de/0x680
[86220.125895] #1: ((addr_chk_work).work){+.+.}, at: [<00000000da8e9b73>] process_one_work+0x1de/0x680
[86220.125959] #2: (rtnl_mutex){+.+.}, at: [<00000000b06d9510>] rtnl_lock+0x12/0x20
[86220.126017] #3: (rcu_read_lock_bh){....}, at: [<00000000aef52299>] addrconf_verify_rtnl+0x1e/0x510 [ipv6]
[86220.126111]
stack backtrace:
[86220.126142] CPU: 0 PID: 1003 Comm: kworker/0:2 Not tainted 4.15.0-rc7-next-20180110+ #7
[86220.126185] Hardware name: ZOTAC ZBOX-CI321NANO/ZBOX-CI321NANO, BIOS B246P105 06/01/2015
[86220.126250] Workqueue: ipv6_addrconf addrconf_verify_work [ipv6]
[86220.126288] Call Trace:
[86220.126312] dump_stack+0x70/0x9e
[86220.126337] lockdep_rcu_suspicious+0xce/0xf0
[86220.126365] ___might_sleep+0x1d3/0x240
[86220.126390] __might_sleep+0x45/0x80
[86220.126416] kmem_cache_alloc_trace+0x53/0x250
[86220.126458] ? ipv6_add_addr+0xfe/0x6e0 [ipv6]
[86220.126498] ipv6_add_addr+0xfe/0x6e0 [ipv6]
[86220.126538] ipv6_create_tempaddr+0x24d/0x430 [ipv6]
[86220.126580] ? ipv6_create_tempaddr+0x24d/0x430 [ipv6]
[86220.126623] addrconf_verify_rtnl+0x339/0x510 [ipv6]
[86220.126664] ? addrconf_verify_rtnl+0x339/0x510 [ipv6]
[86220.126708] addrconf_verify_work+0xe/0x20 [ipv6]
[86220.126738] process_one_work+0x258/0x680
[86220.126765] worker_thread+0x35/0x3f0
[86220.126790] kthread+0x124/0x140
[86220.126813] ? process_one_work+0x680/0x680
[86220.126839] ? kthread_create_worker_on_cpu+0x40/0x40
[86220.126869] ? umh_complete+0x40/0x40
[86220.126893] ? call_usermodehelper_exec_async+0x12a/0x160
[86220.126926] ret_from_fork+0x4b/0x60
[86220.126999] BUG: sleeping function called from invalid context at mm/slab.h:420
[86220.127041] in_atomic(): 1, irqs_disabled(): 0, pid: 1003, name: kworker/0:2
[86220.127082] 4 locks held by kworker/0:2/1003:
[86220.127107] #0: ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<00000000da8e9b73>] process_one_work+0x1de/0x680
[86220.127179] #1: ((addr_chk_work).work){+.+.}, at: [<00000000da8e9b73>] process_one_work+0x1de/0x680
[86220.127242] #2: (rtnl_mutex){+.+.}, at: [<00000000b06d9510>] rtnl_lock+0x12/0x20
[86220.127300] #3: (rcu_read_lock_bh){....}, at: [<00000000aef52299>] addrconf_verify_rtnl+0x1e/0x510 [ipv6]
[86220.127414] CPU: 0 PID: 1003 Comm: kworker/0:2 Not tainted 4.15.0-rc7-next-20180110+ #7
[86220.127463] Hardware name: ZOTAC ZBOX-CI321NANO/ZBOX-CI321NANO, BIOS B246P105 06/01/2015
[86220.127528] Workqueue: ipv6_addrconf addrconf_verify_work [ipv6]
[86220.127568] Call Trace:
[86220.127591] dump_stack+0x70/0x9e
[86220.127616] ___might_sleep+0x14d/0x240
[86220.127644] __might_sleep+0x45/0x80
[86220.127672] kmem_cache_alloc_trace+0x53/0x250
[86220.127717] ? ipv6_add_addr+0xfe/0x6e0 [ipv6]
[86220.127762] ipv6_add_addr+0xfe/0x6e0 [ipv6]
[86220.127807] ipv6_create_tempaddr+0x24d/0x430 [ipv6]
[86220.127854] ? ipv6_create_tempaddr+0x24d/0x430 [ipv6]
[86220.127903] addrconf_verify_rtnl+0x339/0x510 [ipv6]
[86220.127950] ? addrconf_verify_rtnl+0x339/0x510 [ipv6]
[86220.127998] addrconf_verify_work+0xe/0x20 [ipv6]
[86220.128032] process_one_work+0x258/0x680
[86220.128063] worker_thread+0x35/0x3f0
[86220.128091] kthread+0x124/0x140
[86220.128117] ? process_one_work+0x680/0x680
[86220.128146] ? kthread_create_worker_on_cpu+0x40/0x40
[86220.128180] ? umh_complete+0x40/0x40
[86220.128207] ? call_usermodehelper_exec_async+0x12a/0x160
[86220.128243] ret_from_fork+0x4b/0x60

Fixes: f3d9832e56c4 ("ipv6: addrconf: cleanup locking in ipv6_add_addr")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/addrconf.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4352,9 +4352,11 @@ restart:
spin_lock(&ifpub->lock);
ifpub->regen_count = 0;
spin_unlock(&ifpub->lock);
+ rcu_read_unlock_bh();
ipv6_create_tempaddr(ifpub, ifp, true);
in6_ifa_put(ifpub);
in6_ifa_put(ifp);
+ rcu_read_lock_bh();
goto restart;
}
} else if (time_before(ifp->tstamp + ifp->prefered_lft * HZ - regen_advance * HZ, next))

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