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Date: Wed, 29 May 2013 16:39:40 +0800 From: Cong Wang <amwang@...hat.com> To: Stephen Hemminger <stephen@...workplumber.org> Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net> Subject: Re: [Patch net-next] vxlan: do real refcnt for vn_sock On Tue, 2013-05-28 at 21:41 -0700, Stephen Hemminger wrote: > Why not just fix the requirement to drop rtnl when calling igmp. > The code comes out cleaner and safer as well. Besides you forget to lock the socket before calling _ip_mc_join_group() (and also the order is very important too), your patch doesn't fix the problem I met. The full backtrace is below: [ 114.134123] BUG: unable to handle kernel NULL pointer dereference at 0000000000000068 [ 114.136065] IP: [<ffffffff810a1061>] __lock_acquire+0x9c/0x45d [ 114.136065] PGD 71721067 PUD 70e11067 PMD 0 [ 114.136065] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC [ 114.136065] CPU: 0 PID: 707 Comm: ip Not tainted 3.10.0-rc2+ #1075 [ 114.136065] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 [ 114.136065] task: ffff88006fce2480 ti: ffff88006d9ec000 task.ti: ffff88006d9ec000 [ 114.136065] RIP: 0010:[<ffffffff810a1061>] [<ffffffff810a1061>] __lock_acquire+0x9c/0x45d [ 114.136065] RSP: 0018:ffff88006d9ed6a8 EFLAGS: 00010046 [ 114.136065] RAX: 0000000000000068 RBX: 0000000000000000 RCX: 0000000000000000 [ 114.136065] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000068 [ 114.136065] RBP: ffff88006d9ed708 R08: 0000000000000002 R09: 0000000000000000 [ 114.136065] R10: ffffffff8104f0bb R11: ffffffff8107632b R12: ffff88006fce2480 [ 114.136065] R13: 0000000000000000 R14: 0000000000000002 R15: 0000000000000000 [ 114.136065] FS: 00007fc30cd89740(0000) GS:ffff88007f600000(0000) knlGS:0000000000000000 [ 114.136065] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 114.136065] CR2: 0000000000000068 CR3: 000000006f3a2000 CR4: 00000000000006f0 [ 114.136065] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 114.136065] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 114.136065] Stack: [ 114.136065] ffff88006d9ed6b8 ffffffff00000000 ffff880000000000 000000006fce2480 [ 114.136065] ffffffff00000000 0000000000000068 ffffffff825063d2 0000000000000000 [ 114.136065] ffff88006fce2480 ffffffff81757759 0000000000000002 0000000000000000 [ 114.136065] Call Trace: [ 114.136065] [<ffffffff81757759>] ? lock_sock_nested+0x3c/0x97 [ 114.136065] [<ffffffff810a2162>] lock_acquire+0xfa/0x140 [ 114.136065] [<ffffffff81757759>] ? lock_sock_nested+0x3c/0x97 [ 114.136065] [<ffffffff810a06d4>] ? trace_softirqs_off+0x3b/0xf3 [ 114.136065] [<ffffffff81976a1f>] _raw_spin_lock_bh+0x4a/0x7d [ 114.136065] [<ffffffff81757759>] ? lock_sock_nested+0x3c/0x97 [ 114.136065] [<ffffffff810798db>] ? should_resched+0x9/0x28 [ 114.136065] [<ffffffff81757759>] lock_sock_nested+0x3c/0x97 [ 114.136065] [<ffffffff815e13a1>] vxlan_leave_group+0xc4/0x111 [ 114.136065] [<ffffffff81054dfc>] ? local_bh_enable_ip+0xe/0x10 [ 114.136065] [<ffffffff815e142d>] vxlan_stop+0x3f/0xaa [ 114.136065] [<ffffffff817659ff>] __dev_close_many+0x9c/0xc4 [ 114.136065] [<ffffffff81765af3>] dev_close_many+0x70/0xd8 [ 114.136065] [<ffffffff817697f6>] rollback_registered_many+0xa2/0x1a7 [ 114.136065] [<ffffffff81769a4e>] unregister_netdevice_many+0x19/0x51 [ 114.136065] [<ffffffff817738b5>] rtnl_dellink+0xd0/0xfb [ 114.136065] [<ffffffff81058754>] ? ns_capable+0x4d/0x66 [ 114.136065] [<ffffffff81774aaf>] rtnetlink_rcv_msg+0x19c/0x1ab [ 114.136065] [<ffffffff81774913>] ? __rtnl_unlock+0x17/0x17 [ 114.136065] [<ffffffff817bc7d8>] netlink_rcv_skb+0x42/0x8d [ 114.136065] [<ffffffff817748f5>] rtnetlink_rcv+0x26/0x2d [ 114.136065] [<ffffffff817bb001>] netlink_unicast+0xb7/0x138 [ 114.136065] [<ffffffff817bba6b>] netlink_sendmsg+0x2b8/0x2f2 [ 114.136065] [<ffffffff81752e3e>] sock_sendmsg+0x7f/0xa0 [ 114.136065] [<ffffffff8111ee4d>] ? might_fault+0xa5/0xac [ 114.136065] [<ffffffff8111ee04>] ? might_fault+0x5c/0xac [ 114.136065] [<ffffffff817527ba>] ? move_addr_to_kernel+0x41/0x5a [ 114.136065] [<ffffffff8175db77>] ? verify_iovec+0x5b/0xac [ 114.136065] [<ffffffff81753064>] __sys_sendmsg+0x205/0x2a1 [ 114.136065] [<ffffffff8102c172>] ? __do_page_fault+0x2ee/0x38b [ 114.136065] [<ffffffff8107507a>] ? up_read+0x29/0x2e [ 114.136065] [<ffffffff8116794f>] ? fcheck_files+0xa3/0xe1 [ 114.136065] [<ffffffff81168915>] ? fget_light+0x3a/0xa4 [ 114.136065] [<ffffffff81753f91>] SyS_sendmsg+0x42/0x60 [ 114.136065] [<ffffffff819781c2>] system_call_fastpath+0x16/0x1b [ 114.136065] Code: 00 00 83 3d c1 46 d7 01 00 0f 85 cb 03 00 00 48 c7 c1 1c ef d5 81 48 c7 c2 67 5f d5 81 be fb 0b 00 00 e9 1b 02 00 00 48 8b 45 c8 <48> 81 38 a0 f5 52 82 b8 01 00 00 00 44 0f 44 f0 83 fe 01 77 10 [ 114.136065] RIP [<ffffffff810a1061>] __lock_acquire+0x9c/0x45d [ 114.136065] RSP <ffff88006d9ed6a8> [ 114.136065] CR2: 0000000000000068 [ 114.136065] ---[ end trace 92078b41edbc404d ]--- [ 114.136065] Kernel panic - not syncing: Fatal exception in interrupt -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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