• Anoob Soman's avatar
    packet: Do not call fanout_release from atomic contexts · 2bd624b4
    Anoob Soman authored
    Commit 66644982 ("packet: call fanout_release, while UNREGISTERING a
    netdev"), unfortunately, introduced the following issues.
    
    1. calling mutex_lock(&fanout_mutex) (fanout_release()) from inside
    rcu_read-side critical section. rcu_read_lock disables preemption, most often,
    which prohibits calling sleeping functions.
    
    [  ] include/linux/rcupdate.h:560 Illegal context switch in RCU read-side critical section!
    [  ]
    [  ] rcu_scheduler_active = 1, debug_locks = 0
    [  ] 4 locks held by ovs-vswitchd/1969:
    [  ]  #0:  (cb_lock){++++++}, at: [<ffffffff8158a6c9>] genl_rcv+0x19/0x40
    [  ]  #1:  (ovs_mutex){+.+.+.}, at: [<ffffffffa04878ca>] ovs_vport_cmd_del+0x4a/0x100 [openvswitch]
    [  ]  #2:  (rtnl_mutex){+.+.+.}, at: [<ffffffff81564157>] rtnl_lock+0x17/0x20
    [  ]  #3:  (rcu_read_lock){......}, at: [<ffffffff81614165>] packet_notifier+0x5/0x3f0
    [  ]
    [  ] Call Trace:
    [  ]  [<ffffffff813770c1>] dump_stack+0x85/0xc4
    [  ]  [<ffffffff810c9077>] lockdep_rcu_suspicious+0x107/0x110
    [  ]  [<ffffffff810a2da7>] ___might_sleep+0x57/0x210
    [  ]  [<ffffffff810a2fd0>] __might_sleep+0x70/0x90
    [  ]  [<ffffffff8162e80c>] mutex_lock_nested+0x3c/0x3a0
    [  ]  [<ffffffff810de93f>] ? vprintk_default+0x1f/0x30
    [  ]  [<ffffffff81186e88>] ? printk+0x4d/0x4f
    [  ]  [<ffffffff816106dd>] fanout_release+0x1d/0xe0
    [  ]  [<ffffffff81614459>] packet_notifier+0x2f9/0x3f0
    
    2. calling mutex_lock(&fanout_mutex) inside spin_lock(&po->bind_lock).
    "sleeping function called from invalid context"
    
    [  ] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:620
    [  ] in_atomic(): 1, irqs_disabled(): 0, pid: 1969, name: ovs-vswitchd
    [  ] INFO: lockdep is turned off.
    [  ] Call Trace:
    [  ]  [<ffffffff813770c1>] dump_stack+0x85/0xc4
    [  ]  [<ffffffff810a2f52>] ___might_sleep+0x202/0x210
    [  ]  [<ffffffff810a2fd0>] __might_sleep+0x70/0x90
    [  ]  [<ffffffff8162e80c>] mutex_lock_nested+0x3c/0x3a0
    [  ]  [<ffffffff816106dd>] fanout_release+0x1d/0xe0
    [  ]  [<ffffffff81614459>] packet_notifier+0x2f9/0x3f0
    
    3. calling dev_remove_pack(&fanout->prot_hook), from inside
    spin_lock(&po->bind_lock) or rcu_read-side critical-section. dev_remove_pack()
    -> synchronize_net(), which might sleep.
    
    [  ] BUG: scheduling while atomic: ovs-vswitchd/1969/0x00000002
    [  ] INFO: lockdep is turned off.
    [  ] Call Trace:
    [  ]  [<ffffffff813770c1>] dump_stack+0x85/0xc4
    [  ]  [<ffffffff81186274>] __schedule_bug+0x64/0x73
    [  ]  [<ffffffff8162b8cb>] __schedule+0x6b/0xd10
    [  ]  [<ffffffff8162c5db>] schedule+0x6b/0x80
    [  ]  [<ffffffff81630b1d>] schedule_timeout+0x38d/0x410
    [  ]  [<ffffffff810ea3fd>] synchronize_sched_expedited+0x53d/0x810
    [  ]  [<ffffffff810ea6de>] synchronize_rcu_expedited+0xe/0x10
    [  ]  [<ffffffff8154eab5>] synchronize_net+0x35/0x50
    [  ]  [<ffffffff8154eae3>] dev_remove_pack+0x13/0x20
    [  ]  [<ffffffff8161077e>] fanout_release+0xbe/0xe0
    [  ]  [<ffffffff81614459>] packet_notifier+0x2f9/0x3f0
    
    4. fanout_release() races with calls from different CPU.
    
    To fix the above problems, remove the call to fanout_release() under
    rcu_read_lock(). Instead, call __dev_remove_pack(&fanout->prot_hook) and
    netdev_run_todo will be happy that &dev->ptype_specific list is empty. In order
    to achieve this, I moved dev_{add,remove}_pack() out of fanout_{add,release} to
    __fanout_{link,unlink}. So, call to {,__}unregister_prot_hook() will make sure
    fanout->prot_hook is removed as well.
    
    Fixes: 66644982 ("packet: call fanout_release, while UNREGISTERING a netdev")
    Reported-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarAnoob Soman <anoob.soman@citrix.com>
    Acked-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    2bd624b4
af_packet.c 105 KB