bad dereference in sched_mc_power_savings_store()

[Pierre Ossman]

I get the following with yesterdays kernel:

[   62.650080] BUG: unable to handle kernel NULL pointer dereference at 00000002
[   62.650093] IP: [<c0428736>] sched_mc_power_savings_store+0x6/0x40
[   62.650109] *pdpt = 0000000035447001 *pde = 0000000000000000 
[   62.650119] Oops: 0000 [#2] PREEMPT SMP 
[   62.650127] Modules linked in: ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 xt_state nf_conntrack ipt_REJECT xt_tcpudp iptable_filter ip_tables x_tables bridge stp llc rfcomm l2cap fuse sunrpc ipv6 acpi_cpufreq binfmt_misc loop kvm_intel kvm sr_mod cdrom snd_hda_intel snd_seq_dummy ata_piix pcmcia snd_seq_oss ata_generic snd_seq_midi_event snd_seq arc4 ecb i2c_i801 sdhci_pci snd_seq_device yenta_socket firewire_ohci crypto_blkcipher rtc_cmos sdhci firewire_core snd_pcm_oss rsrc_nonstatic sg rtc_core thinkpad_acpi mmc_core snd_mixer_oss i2c_core pcmcia_core rtc_lib ricoh_mmc ac pcspkr pata_acpi crc_itu_t iwl4965 video snd_pcm output iwlcore battery bay rfkill snd_timer mac80211 snd wmi soundcore hci_usb e1000e button snd_page_alloc bluetooth cfg80211 ahci libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: microcode]
[   62.650292] 
[   62.650298] Pid: 2823, comm: sched-powersave Tainted: G      D   (2.6.26 #108)
[   62.650304] EIP: 0060:[<c0428736>] EFLAGS: 00010286 CPU: 1
[   62.650312] EIP is at sched_mc_power_savings_store+0x6/0x40
[   62.650317] EAX: c076e700 EBX: c0428730 ECX: 00000002 EDX: ffffffea
[   62.650323] ESI: c076e724 EDI: f5546000 EBP: f54aff3c ESP: f54aff28
[   62.650328]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[   62.650334] Process sched-powersave (pid: 2823, ti=f54af000 task=f4ffa400 task.ti=f54af000)
[   62.650338] Stack: f54aff3c c059d930 f740c150 c076e418 f541b2c0 f54aff6c c04e7f32 00000002 
[   62.650355]        00000002 b7fb2000 f587f900 f541b2d4 c076e418 c076e724 f587f900 b7fb2000 
[   62.650370]        00000002 f54aff90 c049f81c f54aff9c 00000001 00000004 c04e7e90 f587f900 
[   62.650385] Call Trace:
[   62.650390]  [<c059d930>] ? sysdev_class_store+0x30/0x40
[   62.650403]  [<c04e7f32>] ? sysfs_write_file+0xa2/0x100
[   62.650414]  [<c049f81c>] ? vfs_write+0x9c/0x160
[   62.650424]  [<c04e7e90>] ? sysfs_write_file+0x0/0x100
[   62.650433]  [<c049f9a2>] ? sys_write+0x42/0x70
[   62.650442]  [<c0403fc6>] ? syscall_call+0x7/0xb
[   62.650451]  =======================
[   62.650455] Code: ff 89 c3 b8 08 e9 75 c0 e8 08 5d 24 00 e8 93 4b 00 00 89 d8 5b c9 c3 8d b4 26 00 00 00 00 8d bc 27 00 00 00 00 55 ba ea ff ff ff <0f> b6 09 89 e5 8d 41 d0 3c 01 76 0e 89 d0 c9 c3 8d 76 00 8d bc 
[   62.650540] EIP: [<c0428736>] sched_mc_power_savings_store+0x6/0x40 SS:ESP 0068:f54aff28
[   62.650560] ---[ end trace 155686795e307d74 ]---

I'm guessing it's because of commit 4a0b2b4dbe.

Rgds
-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  rdesktop, core developer          http://www.rdesktop.org

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