From 9a9c1bae4713a45a2f0be76a41c556012c567542 Mon Sep 17 00:00:00 2001 From: Anoob Soman Date: Wed, 15 Feb 2017 20:25:39 +0000 Subject: [PATCH] packet: Do not call fanout_release from atomic contexts commit 2bd624b4611ffee36422782d16e1c944d1351e98 upstream. Commit 6664498280cf ("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: [] genl_rcv+0x19/0x40 [ ] #1: (ovs_mutex){+.+.+.}, at: [] ovs_vport_cmd_del+0x4a/0x100 [openvswitch] [ ] #2: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ ] #3: (rcu_read_lock){......}, at: [] packet_notifier+0x5/0x3f0 [ ] [ ] Call Trace: [ ] [] dump_stack+0x85/0xc4 [ ] [] lockdep_rcu_suspicious+0x107/0x110 [ ] [] ___might_sleep+0x57/0x210 [ ] [] __might_sleep+0x70/0x90 [ ] [] mutex_lock_nested+0x3c/0x3a0 [ ] [] ? vprintk_default+0x1f/0x30 [ ] [] ? printk+0x4d/0x4f [ ] [] fanout_release+0x1d/0xe0 [ ] [] 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: [ ] [] dump_stack+0x85/0xc4 [ ] [] ___might_sleep+0x202/0x210 [ ] [] __might_sleep+0x70/0x90 [ ] [] mutex_lock_nested+0x3c/0x3a0 [ ] [] fanout_release+0x1d/0xe0 [ ] [] 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: [ ] [] dump_stack+0x85/0xc4 [ ] [] __schedule_bug+0x64/0x73 [ ] [] __schedule+0x6b/0xd10 [ ] [] schedule+0x6b/0x80 [ ] [] schedule_timeout+0x38d/0x410 [ ] [] synchronize_sched_expedited+0x53d/0x810 [ ] [] synchronize_rcu_expedited+0xe/0x10 [ ] [] synchronize_net+0x35/0x50 [ ] [] dev_remove_pack+0x13/0x20 [ ] [] fanout_release+0xbe/0xe0 [ ] [] 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: 6664498280cf ("packet: call fanout_release, while UNREGISTERING a netdev") Reported-by: Eric Dumazet Signed-off-by: Anoob Soman Acked-by: Eric Dumazet Signed-off-by: David S. Miller [bwh: Backported to 3.2: - Don't call fanout_release_data() - Adjust context] Signed-off-by: Ben Hutchings --- Reading git-format-patch failed