[Bug 49087] Segmentation faults when balancing load betwenn 2 network links

[Jorge Suarez]

Public bug reported:

I have two upstream providers at work, and at home too, i set up 2 load
balancing to the internet this way

ip route add default nexthop via $provider1gw weight 2 nexthop via
$provider2gw weight 1

I've done so since warty, never had an issue and works fine. 
Since I installed dapper I have had some inestability issues with this, especially when using azureus and gaim, upon startup (both at home and at work, different PCs) they are giving me segfaults, and partial system lockups.

After either of these crashes, i have the following when i type dmesg:

[4294874.014000] Unable to handle kernel NULL pointer dereference at virtual add ress 00000094
[4294874.014000]  printing eip:
[4294874.014000] c029db1d
[4294874.014000] *pde = 00000000
[4294874.014000] Oops: 0000 [#1]
[4294874.014000] PREEMPT
[4294874.014000] Modules linked in: wlan_tkip af_packet nls_cp437 isofs udf binf mt_misc rfcomm l2cap bluetooth vmnet vmmon ppdev speedstep_lib cpufreq_userspace  cpufreq_stats freq_table cpufreq_powersave cpufreq_ondemand cpufreq_conservativ e video toshiba_acpi tc1100_wmi sony_acpi pcc_acpi hotkey dev_acpi container but ton acpi_sbs battery ac i2c_acpi_ec ipv6 dm_mod md_mod lp pcmcia 8139cp yenta_so cket rsrc_nonstatic rtc pcmcia_core parport_pc joydev tsdev parport psmouse seri o_raw 8139too mii pcspkr ath_pci ath_rate_sample wlan ath_hal snd_ali5451 snd_ac 97_codec snd_ac97_bus i2c_ali1535 i2c_ali15x3 snd_pcm_oss snd_mixer_oss shpchp p ci_hotplug ali_agp i2c_core snd_pcm snd_timer agpgart snd soundcore snd_page_all oc evdev ext3 jbd ide_generic ehci_hcd ohci_hcd usbcore ide_cd cdrom ide_disk ge neric alim15x3 thermal processor fan capability commoncap vesafb fbcon tileblit font bitblit softcursor
[4294874.014000] CPU:    0
[4294874.014000] EIP:    0060:[<c029db1d>]    Tainted: P      VLI
[4294874.014000] EFLAGS: 00210297   (2.6.15-23-386)
[4294874.014000] EIP is at ip_route_output_slow+0x38d/0xe00
[4294874.014000] eax: 0000000b   ebx: 00000001   ecx: 00000000   edx: c3f32401
[4294874.014000] esi: 00000000   edi: c4d30000   ebp: 00000000   esp: c4b1fc80
[4294874.014000] ds: 007b   es: 007b   ss: 0068
[4294874.014000] Process gaim (pid: 5822, threadinfo=c4b1e000 task=c4c15550)
[4294874.014000] Stack: 20000000 c4d30000 00000001 00000000 c3f32480 0262a6ec 00 000000 00000001
[4294874.014000]        00000000 00000002 00000001 faffffef 9801a8c0 00000000 00 000000 00000000
[4294874.014000]        00000000 00000000 00000000 00000000 00000000 00000000 00 000000 00000000
[4294874.014000] Call Trace:
[4294874.014000]  [<c029e6db>] ip_route_output_flow+0x1b/0x80
[4294874.014000]  [<c02c182f>] udp_sendmsg+0x51f/0x6d0
[4294874.014000]  [<c0274dca>] sock_sendmsg+0xea/0x120
[4294874.014000]  [<c0131170>] autoremove_wake_function+0x0/0x40
[4294874.014000]  [<c01406db>] __generic_file_aio_read+0x9b/0x230
[4294874.014000]  [<c014ee61>] zap_pte_range+0x181/0x2a0
[4294874.014000]  [<c02763e8>] sys_sendto+0xf8/0x150
[4294874.014000]  [<c0155979>] page_add_file_rmap+0x39/0x50
[4294874.014000]  [<c0150bd1>] do_no_page+0x161/0x2d0
[4294874.014000]  [<c0150e65>] __handle_mm_fault+0xa5/0x210
[4294874.014000]  [<c0276d26>] sys_socketcall+0x156/0x1e0
[4294874.014000]  [<c010302b>] sysenter_past_esp+0x54/0x79
[4294874.014000] Code: 8a 44 24 17 48 25 ff 00 00 00 40 39 44 24 1c 0f 84 ae 00 00 00 8b 4c 24 78 8a 54 24 1c 88 54 24 6d 8b 5c 24 1c 8d 04 9b 8d 04 43 <8b> 7c 81 68 ff 87 58 01 00 00 84 d2 74 1b 8b 84 24 94 00 00 00

I think it's iproute2 related, for what i read on the first line, after
it happens some applications, like gdebi for instance won't start.

** Affects: linux-source-2.6.15 (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed

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Segmentation faults when balancing load betwenn 2 network links
https://launchpad.net/bugs/49087