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Message-ID: <CA+1xoqdi4QOhRJvBA64pxiN3EphhThjPkf4eLRkYM8jxcJjh=w@mail.gmail.com> Date: Fri, 6 Apr 2012 11:04:25 +0200 From: Sasha Levin <levinsasha928@...il.com> To: "Eric W. Biederman" <ebiederm@...ssion.com> Cc: davem <davem@...emloft.net>, Eric Dumazet <eric.dumazet@...il.com>, Eric Van Hensbergen <ericvh@...il.com>, Dave Jones <davej@...hat.com>, linux-kernel <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org> Subject: Re: net: kernel BUG() in net/netns/generic.h:45 On Fri, Apr 6, 2012 at 1:53 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote: > Sasha Levin <levinsasha928@...il.com> writes: > >> Hi all, >> >> When an initialization of a network namespace in setup_net() fails, we >> try to undo everything by executing each of the exit callbacks of every >> namespace in the network. >> >> The problem is, it might be possible that the net_generic array wasn't >> initialized before we fail and try to undo everything. At that point, >> some of the networks assume that since we're already calling the exit >> callback, the net_generic structure is initialized and we hit the BUG() >> in net/netns/generic.h:45 . >> >> I'm not quite sure whether the right fix from the following three >> options is, and would be happy to figure it out before fixing it: >> >> 1. Don't assume net_generic was initialized in the exit callback, which >> is a bit problematic since we can't query that nicely anyway (a >> sub-option here would be adding an API to query whether the net_generic >> structure is initialized. >> >> 2. Remove the BUG(), switch it to a WARN() and let each subsystem >> handle the case of NULL on it's own. While it sounds a bit wrong, it's >> worth mentioning that that BUG() was initially added in an attempt to >> fix an issue in CAIF, which was fixed in a completely different way >> afterwards, so it's not strictly necessary here. >> >> 3. Only call the exit callback for subsystems we have called the init >> callback for. > > Your option 3 only calling the exit callbacks for subsystems we have > initialized should be what is implemented. Certainly it looks like we > are attempting to only call the exit callbacks for code whose init > callback has succeeded. > > What problem are you seeing? > > This smells suspiciously like a problem we had a little while ago caif > was registering as a pernet device instead of a pernet subsystem, > and because of that we had packets flying around after it had been > unregistered and was trying access it's net_generic data. It looks different from the caif problem a bit, here is a sample stacktrace: [ 163.733755] ------------[ cut here ]------------ [ 163.734501] kernel BUG at include/net/netns/generic.h:45! [ 163.734501] invalid opcode: 0000 [#1] PREEMPT SMP [ 163.734501] CPU 2 [ 163.734501] Pid: 19145, comm: trinity Tainted: G W 3.4.0-rc1-next-20120405-sasha-dirty #57 [ 163.734501] RIP: 0010:[<ffffffff824d6062>] [<ffffffff824d6062>] phonet_pernet+0x182/0x1a0 [ 163.734501] RSP: 0018:ffff8800674d5ca8 EFLAGS: 00010246 [ 163.734501] RAX: 000000003fffffff RBX: 0000000000000000 RCX: ffff8800678c88d8 [ 163.734501] RDX: 00000000003f4000 RSI: ffff8800678c8910 RDI: 0000000000000282 [ 163.734501] RBP: ffff8800674d5cc8 R08: 0000000000000000 R09: 0000000000000000 [ 163.734501] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880068bec920 [ 163.734501] R13: ffffffff836b90c0 R14: 0000000000000000 R15: 0000000000000000 [ 163.734501] FS: 00007f055e8de700(0000) GS:ffff88007d000000(0000) knlGS:0000000000000000 [ 163.734501] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 163.734501] CR2: 00007f055e6bb518 CR3: 0000000070c16000 CR4: 00000000000406e0 [ 163.734501] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 163.734501] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 163.734501] Process trinity (pid: 19145, threadinfo ffff8800674d4000, task ffff8800678c8000) [ 163.734501] Stack: [ 163.734501] ffffffff824d5f00 ffffffff810e2ec1 ffff880067ae0000 00000000ffffffd4 [ 163.734501] ffff8800674d5cf8 ffffffff824d667a ffff880067ae0000 00000000ffffffd4 [ 163.734501] ffffffff836b90c0 0000000000000000 ffff8800674d5d18 ffffffff824d707d [ 163.734501] Call Trace: [ 163.734501] [<ffffffff824d5f00>] ? phonet_pernet+0x20/0x1a0 [ 163.734501] [<ffffffff810e2ec1>] ? get_parent_ip+0x11/0x50 [ 163.734501] [<ffffffff824d667a>] phonet_device_destroy+0x1a/0x100 [ 163.734501] [<ffffffff824d707d>] phonet_device_notify+0x3d/0x50 [ 163.734501] [<ffffffff810dd96e>] notifier_call_chain+0xee/0x130 [ 163.734501] [<ffffffff810dd9d1>] raw_notifier_call_chain+0x11/0x20 [ 163.734501] [<ffffffff821cce12>] call_netdevice_notifiers+0x52/0x60 [ 163.734501] [<ffffffff821cd235>] rollback_registered_many+0x185/0x270 [ 163.734501] [<ffffffff821cd334>] unregister_netdevice_many+0x14/0x60 [ 163.734501] [<ffffffff823123e3>] ipip_exit_net+0x1b3/0x1d0 [ 163.734501] [<ffffffff82312230>] ? ipip_rcv+0x420/0x420 [ 163.734501] [<ffffffff821c8515>] ops_exit_list+0x35/0x70 [ 163.734501] [<ffffffff821c911b>] setup_net+0xab/0xe0 [ 163.734501] [<ffffffff821c9416>] copy_net_ns+0x76/0x100 [ 163.734501] [<ffffffff810dc92b>] create_new_namespaces+0xfb/0x190 [ 163.734501] [<ffffffff810dca21>] unshare_nsproxy_namespaces+0x61/0x80 [ 163.734501] [<ffffffff810afd1f>] sys_unshare+0xff/0x290 [ 163.734501] [<ffffffff8187622e>] ? trace_hardirqs_on_thunk+0x3a/0x3f [ 163.734501] [<ffffffff82665539>] system_call_fastpath+0x16/0x1b [ 163.734501] Code: e0 c3 fe 66 0f 1f 44 00 00 48 c7 c2 40 60 4d 82 be 01 00 00 00 48 c7 c7 80 d1 23 83 e8 48 2a c4 fe e8 73 06 c8 fe 48 85 db 75 0e <0f> 0b 0f 1f 40 00 eb fe 66 0f 1f 44 00 00 48 83 c4 10 48 89 d8 [ 163.734501] RIP [<ffffffff824d6062>] phonet_pernet+0x182/0x1a0 [ 163.734501] RSP <ffff8800674d5ca8> [ 163.861289] ---[ end trace fb5615826c548066 ]--- It would appear that there's at least a one-off problem with the reverse iteration. -- 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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