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Message-ID: <20131204132843.GB4096@hmsreliant.think-freely.org> Date: Wed, 4 Dec 2013 08:28:43 -0500 From: Neil Horman <nhorman@...driver.com> To: Vlad Yasevich <vyasevich@...il.com> Cc: Wang Weidong <wangweidong1@...wei.com>, David Miller <davem@...emloft.net>, netdev@...r.kernel.org, linux-sctp@...r.kernel.org Subject: Re: [PATCH] sctp: fix a BUG_ON on triggered by setting max_autoclose to On Tue, Dec 03, 2013 at 04:24:10PM -0500, Vlad Yasevich wrote: > On 12/03/2013 01:18 PM, Neil Horman wrote: > > On Tue, Dec 03, 2013 at 11:09:38AM -0500, Vlad Yasevich wrote: > >> On 12/03/2013 05:09 AM, Wang Weidong wrote: > >>> since 2692ba61, add the max_autoclose to sysctl. when I setted the > >>> max_autoclose to 0. Just do the test_autoclose, it will trigger that: > >>> > >>> [ 608.056238] ------------[ cut here ]------------ > >>> [ 608.056244] kernel BUG at /home/wwd/work/linux/net/sctp/sm_sideeffect.c:1488! > >>> [ 608.056250] invalid opcode: 0000 [#1] SMP > >>> [ 608.056254] Modules linked in: md5 sctp(O) crc32c libcrc32c edd fuse loop dm_mod ipv6 8139too sg 8139cp mii i2c_piix4 i2c_core virtio_balloon intel_agp virtio_pci virtio_ring sr_mod cdrom rtc_cmos joydev hid_generic intel_gtt virtio floppy pcspkr button ext3 jbd mbcache usbhid hid uhci_hcd ehci_hcd usbcore sd_mod usb_common crc_t10dif crct10dif_common processor thermal_sys hwmon scsi_dh_emc scsi_dh_alua scsi_dh_hp_sw scsi_dh_rdac scsi_dh ata_generic ata_piix libata scsi_mod [last unloaded: sctp] > >>> [ 608.056310] CPU: 5 PID: 4517 Comm: test_autoclose Tainted: G R O 3.13.0-rc1-0.27-default+ #2 > >>> [ 608.056315] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 > >>> [ 608.056319] task: ffff8800372f5590 ti: ffff8800db882000 task.ti: ffff8800db882000 > >>> [ 608.056323] RIP: 0010:[<ffffffffa033e350>] [<ffffffffa033e350>] sctp_cmd_interpreter+0x1010/0x1070 [sctp] > >>> [ 608.056339] RSP: 0018:ffff880116f43928 EFLAGS: 00010246 > >>> [ 608.056343] RAX: 0000000000000009 RBX: ffff880116f43ab8 RCX: 0000000000000009 > >>> [ 608.056349] RDX: 0000000000000003 RSI: 0000000000000000 RDI: ffff880116f43a88 > >>> [ 608.056353] RBP: ffff880116f439d8 R08: 0000000000002029 R09: 0000000000000001 > >>> [ 608.056357] R10: 0000000000000000 R11: 0000000000000005 R12: ffff8800db7c9150 > >>> [ 608.056361] R13: 0000000000000000 R14: ffff8800db7c9000 R15: 0000000000000001 > >>> [ 608.056365] FS: 00007f942d71c700(0000) GS:ffff880116f40000(0000) knlGS:0000000000000000 > >>> [ 608.056370] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > >>> [ 608.056373] CR2: 00007f942d324d90 CR3: 00000000db094000 CR4: 00000000000006e0 > >>> [ 608.056382] Stack: > >>> [ 608.056384] 0000000000000018 ffff880116f43988 ffff8800da569600 000000010000000a > >>> [ 608.056391] ffff880037265e40 0000000016f43988 ffff880116f439e8 0000000000000000 > >>> [ 608.056397] ffffffffa0365101 0000000000000000 ffff880116f43a28 ffffffff812b7739 > >>> [ 608.056403] Call Trace: > >>> [ 608.056406] <IRQ> > >>> [ 608.056409] > >>> [ 608.056421] [<ffffffff812b7739>] ? __dynamic_pr_debug+0x69/0x80 > >>> [ 608.056432] [<ffffffff81097c6d>] ? trace_hardirqs_off+0xd/0x10 > >>> [ 608.056442] [<ffffffff814e7258>] ? _raw_spin_unlock_irqrestore+0x58/0x60 > >>> [ 608.056451] [<ffffffffa033e3e6>] sctp_side_effects+0x36/0x130 [sctp] > >>> [ 608.056459] [<ffffffffa033e5c7>] sctp_do_sm+0xe7/0x210 [sctp] > >>> [ 608.056470] [<ffffffffa0359860>] ? sctp_rcv+0x780/0x780 [sctp] > >>> [ 608.056479] [<ffffffffa0340a5f>] sctp_endpoint_bh_rcv+0x10f/0x220 [sctp] > >>> [ 608.056489] [<ffffffffa0349991>] sctp_inq_push+0x41/0x60 [sctp] > >>> [ 608.056498] [<ffffffffa03597b5>] sctp_rcv+0x6d5/0x780 [sctp] > >>> [ 608.056508] [<ffffffffa0358e00>] ? sctp_csum_combine+0x10/0x10 [sctp] > >>> [ 608.056518] [<ffffffffa0358df0>] ? sctp_v4_err+0x240/0x240 [sctp] > >>> [ 608.056528] [<ffffffff8145b8a4>] ip_local_deliver_finish+0xf4/0x270 > >>> [ 608.056533] [<ffffffff8145b7f0>] ? ip_local_deliver_finish+0x40/0x270 > >>> [ 608.056538] [<ffffffff8145b690>] ip_local_deliver+0x80/0x90 > >>> [ 608.056543] [<ffffffff8145bbd3>] ip_rcv_finish+0x1b3/0x600 > >>> [ 608.056547] [<ffffffff8145ba20>] ? ip_local_deliver_finish+0x270/0x270 > >>> [ 608.056552] [<ffffffff8145b04f>] NF_HOOK+0x2f/0x70 > >>> [ 608.056565] [<ffffffff81425853>] ? __netif_receive_skb_core+0x113/0x7a0 > >>> [ 608.056570] [<ffffffff8145b365>] ip_rcv+0x2d5/0x3b0 > >>> [ 608.056575] [<ffffffff81425e3f>] __netif_receive_skb_core+0x6ff/0x7a0 > >>> [ 608.056580] [<ffffffff81425853>] ? __netif_receive_skb_core+0x113/0x7a0 > >>> [ 608.056585] [<ffffffff81426108>] ? process_backlog+0x1a8/0x1c0 > >>> [ 608.056590] [<ffffffff81425f0b>] __netif_receive_skb+0x2b/0x80 > >>> [ 608.056595] [<ffffffff81426018>] process_backlog+0xb8/0x1c0 > >>> [ 608.056600] [<ffffffff8142695c>] net_rx_action+0x11c/0x240 > >>> [ 608.056607] [<ffffffff81050e18>] __do_softirq+0x118/0x290 > >>> [ 608.056615] [<ffffffff814f0e0c>] do_softirq_own_stack+0x1c/0x30 > >>> [ 608.056618] <EOI> > >>> [ 608.056620] > >>> [ 608.056623] [<ffffffff81050bd5>] do_softirq+0x65/0x70 > >>> [ 608.056629] [<ffffffff8140fddc>] ? release_sock+0x8c/0xa0 > >>> [ 608.056635] [<ffffffff810518c3>] local_bh_enable_ip+0xb3/0xc0 > >>> [ 608.056640] [<ffffffff814e71af>] _raw_spin_unlock_bh+0x2f/0x40 > >>> [ 608.056645] [<ffffffff8140fddc>] release_sock+0x8c/0xa0 > >>> [ 608.056654] [<ffffffffa0354c08>] sctp_sendmsg+0x3a8/0xcc0 [sctp] > >>> [ 608.056661] [<ffffffff8129924a>] ? number+0x33a/0x360 > >>> [ 608.056667] [<ffffffff81497c3c>] inet_sendmsg+0x9c/0x100 > >>> [ 608.056672] [<ffffffff81497ba0>] ? inet_recvmsg+0x110/0x110 > >>> [ 608.056679] [<ffffffff8140a387>] sock_sendmsg+0x97/0xc0 > >>> [ 608.056690] [<ffffffff8114caae>] ? might_fault+0x3e/0x90 > >>> [ 608.056695] [<ffffffff8114caae>] ? might_fault+0x3e/0x90 > >>> [ 608.056700] [<ffffffff81417a73>] ? verify_iovec+0x53/0x100 > >>> [ 608.056705] [<ffffffff8140abb6>] ___sys_sendmsg+0x416/0x420 > >>> [ 608.056710] [<ffffffff81151af6>] ? __do_fault+0x216/0x510 > >>> [ 608.056715] [<ffffffff814eaf74>] ? __do_page_fault+0x2b4/0x4a0 > >>> [ 608.056720] [<ffffffff81095c9e>] ? up_read+0x1e/0x40 > >>> [ 608.056724] [<ffffffff814eaf74>] ? __do_page_fault+0x2b4/0x4a0 > >>> [ 608.056729] [<ffffffff8140fddc>] ? release_sock+0x8c/0xa0 > >>> [ 608.056733] [<ffffffff8140fddc>] ? release_sock+0x8c/0xa0 > >>> [ 608.056741] [<ffffffff8109bb5d>] ? trace_hardirqs_on+0xd/0x10 > >>> [ 608.056746] [<ffffffff81051875>] ? local_bh_enable_ip+0x65/0xc0 > >>> [ 608.056751] [<ffffffff8140ad94>] __sys_sendmsg+0x44/0x80 > >>> [ 608.056756] [<ffffffff8140ade4>] SyS_sendmsg+0x14/0x20 > >>> [ 608.056761] [<ffffffff814ef5a2>] system_call_fastpath+0x16/0x1b > >>> ------------------------------------- > >>> > >>> The reason is: In test_autoclose set the autoclose to 5 not 0(default). So when > >>> we init the association, the (sctp_sock) sp->autoclose is not 0 while asoc's > >>> timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] is 0. > >>> So when we process the COOKIE_ACK, the sctp_sf_do_5_1E_ca will be called, that > >>> will do that: > >>> if (asoc->autoclose) //asoc->autoclose is equal sp->autoclose > >>> sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_START, > >>> SCTP_TO(SCTP_EVENT_TIMEOUT_AUTOCLOSE)); > >> > >> this looks like a bug in how the timeout is being set. The timeout > >> should be based on the association value, not some sysctl value. > >> > >> The typical socket option values go like this: > >> socket value = starts at sysctl, changed by user. > >> assoc value = starts at socket value, may be changed by user. > >> any timer = starts at assoc value. > >> > >> this seems to be broken for autoclose. > >> > > Well, it is, but I think its a reasonable fix for the issue. As I understand > > the description, the problem is that if autoclose is non-zero, and the default > > timeout is zero, then you'll get a BUG_ON halt because you need to set a timer > > that will expire immediately. It seems reasonable to me to make a minimal > > default for the timeout to be non-zero, since it makes no sense to have a zero > > auto-close timeout. > > Yes, the default timeout is zero because the timeout is latched by the > sysctl value while the association value is not. So, the association > value is now out-of-sync with what the system does and we end up lying > to the user when they do a getsockopt(). > Thats not true, looking at the sctp_association_init code the timeout is defaulted to the minimum of the socket value and the maxium timeout sysctl value, the latter of which is defined as INT_MAX/HZ. That seems reasonable to me in that an association latches both the timeout value and the enabled value from its parent socket at association init time (assoc->autoclose is assigned from sp->autoclose farther down in sctp_association_init). > If we simply latch the socket value properly, then we would have to > worry about this at all. If the socket value is latched at 0, then > autoclose is disabled. > We are latching the value properly from what I can see. The problem is that the upper bound on the value we latch can be zero. The only way this bug can occur is if net->sctp.max_autoclose is 0. Note that I'm not talking about the timeout value itself, but its upper bound. We shouldn't be allowed to set the autoclose timeout sysctl range to [0..0], it just doesn't make sense. It should be at least [0..1], and the socket autoclose value can range properly within that. >From what I see, thats what this patch does. Neil -- 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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