[Xen-devel] Null-pointer access in netback_uevent

[Bastian Blank <waldi@xxxxxxxxxx>]

My slightly patched kernel based on
f6fe6583b77a49b569eef1b66c3d761eec2e561b failed with null-pointer access in
netback_uevent.

| BUG: unable to handle kernel NULL pointer dereference at 0000000000000150
| IP: [<ffffffff812017a3>] netback_uevent+0x83/0xaf

According to gdb the following is the culprit:

| 185             if (add_uevent_var(env, "vif=%s", netif->dev->name))
|    0x0000000000002313 <+131>:   mov    0x150(%r13),%rdx

Complete oops:

| BUG: unable to handle kernel NULL pointer dereference at 0000000000000150
| IP: [<ffffffff812017a3>] netback_uevent+0x83/0xaf
| PGD ce0b1067 PUD ce193067 PMD 0 
| Oops: 0000 [#1] SMP 
| last sysfs file: /sys/devices/vif-1-0/uevent
| CPU 1 
| Modules linked in: blktap xen_evtchn xenfs xt_tcpudp xt_state iptable_filter 
ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 
ip_tables x_tables bridge stp dm_snapshot loop snd_pcm snd_timer snd soundcore 
tpm_tis radeon snd_page_alloc ttm drm_kms_helper psmouse tpm drm pcspkr 
amd64_edac_mod ipmi_si tpm_bios evdev serio_raw edac_core i2c_algo_bit shpchp 
ipmi_msghandler i2c_piix4 edac_mce_amd container i2c_core hpilo processor 
pci_hotplug button acpi_processor hpwdt ext3 jbd mbcache dm_mod cciss 
ata_generic libata scsi_mod bnx2 thermal thermal_sys [last unloaded: xen_evtchn]
| Pid: 8076, comm: udevd Tainted: G        W  2.6.32-5-xen-amd64 #2 ProLiant 
DL385 G6   
| RIP: e030:[<ffffffff812017a3>]  [<ffffffff812017a3>] netback_uevent+0x83/0xaf
| RSP: e02b:ffff880002af7e18  EFLAGS: 00010246
| RAX: 01000000000000c1 RBX: ffff8800029f6000 RCX: 0000000000800078
| RDX: ffff8800c33b13a0 RSI: ffffea0002ab4eb8 RDI: 01000000000002c0
| RBP: ffff8800c33b14e0 R08: 0000000000000000 R09: ffffffff814664f0
| R10: 0000000000000200 R11: ffffffff8100f19c R12: ffff880002f39c00
| R13: 0000000000000000 R14: ffff8800021db000 R15: ffff8800c5026980
| FS:  00007fbd86ad2790(0000) GS:ffff880003a64000(0000) knlGS:0000000000000000
| CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
| CR2: 0000000000000150 CR3: 00000000025f4000 CR4: 0000000000000660
| DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
| DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
| Process udevd (pid: 8076, threadinfo ffff880002af6000, task ffff88000246c6a0)
| Stack:
|  0000000000000908 ffff880002f39c40 ffff8800029f6000 ffff8800c3795c30
|  ffff8800029f6000 ffffffff8122d9f6 ffff880002f39c50 ffff8800c3795c30
|  ffffffff814a80d0 0000000000000000 ffff880002f39c50 ffffffff8122db35
| Call Trace:
|  [<ffffffff8122d9f6>] ? dev_uevent+0x104/0x146
|  [<ffffffff8122db35>] ? show_uevent+0x81/0xd5
|  [<ffffffff8122d6da>] ? dev_attr_show+0x1f/0x42
|  [<ffffffff8114074f>] ? sysfs_read_file+0xa7/0x125
|  [<ffffffff810f0a6e>] ? vfs_read+0xa6/0xff
|  [<ffffffff810f0b83>] ? sys_read+0x45/0x6e
|  [<ffffffff81011b42>] ? system_call_fastpath+0x16/0x1b
| Code: c7 c6 fe 1c 3f 81 31 c0 48 89 df e8 44 fe f8 ff 85 c0 74 0f 48 89 ef bb 
f4 ff ff ff e8 39 70 ee ff eb 2a 48 89 ef e8 2f 70 ee ff <49> 8b 95 50 01 00 00 
48 89 df 31 c0 48 c7 c6 08 1d 3f 81 e8 11 
| RIP  [<ffffffff812017a3>] netback_uevent+0x83/0xaf
|  RSP <ffff880002af7e18>
| CR2: 0000000000000150
| ---[ end trace a7919e7f17c0a727 ]---

Bastian

-- 
Men will always be men -- no matter where they are.
                -- Harry Mudd, "Mudd's Women", stardate 1329.8

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