Re: [PATCH 2/2] power: Change device_wakeup_enable() to WARN_ON on null dev_name(dev)

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Nov 19, 2013 at 04:52:59PM -0700, Shuah Khan wrote:
> On 11/19/2013 04:56 PM, Rafael J. Wysocki wrote:
> > On Tuesday, November 19, 2013 03:14:01 PM Greg KH wrote:
> >> On Tue, Nov 19, 2013 at 09:05:46AM -0700, Shuah Khan wrote:
> >>> device_wakeup_enable() uses dev_name(dev) as the wakeup source name.
> >>> When it gets called with a device with its name not yet set, ws structure
> >>> with ws->name = NULL gets created.
> >>>
> >>> When kernel is booted with wakeup_source_activate enabled, it will panic
> >>> when the trace point code tries to dereferences ws->name.
> >>>
> >>> Change device_wakeup_enable() to WARN_ON on dev_name(dev) null condition
> >>> to detect driver bugs that result in calling device_wakeup_enable() before
> >>> device is fully initialized with its name in device_wakeup_enable().
> >>>
> >>> This change without the power_supply_register() fix will result in early
> >>> boot panics when AC Adapter and Battery device drivers try to register
> >>> wakeup source.
> >>>
> >>> The following panic resulted from power_supply_register() registering
> >>> wakeup source with a null device name.
> >>>
> >>> [  819.769934] device: 'BAT1': device_add
> >>> [  819.770078] PM: Adding info for No Bus:BAT1
> >>> [  819.770235] BUG: unable to handle kernel NULL pointer dereference at           (null)
> >>> [  819.770435] IP: [<ffffffff813381c0>] skip_spaces+0x30/0x30
> >>> [  819.770572] PGD 3efd90067 PUD 3eff61067 PMD 0
> >>> [  819.770716] Oops: 0000 [#1] SMP
> >>> [  819.770829] Modules linked in: arc4 iwldvm mac80211 x86_pkg_temp_thermal coretemp kvm_intel joydev i915 kvm uvcvideo ghash_clmulni_intel videobuf2_vmalloc aesni_intel videobuf2_memops videobuf2_core aes_x86_64 ablk_helper cryptd videodev iwlwifi lrw rfcomm gf128mul glue_helper bnep btusb media bluetooth parport_pc hid_generic ppdev snd_hda_codec_hdmi drm_kms_helper snd_hda_codec_realtek cfg80211 drm tpm_infineon samsung_laptop snd_hda_intel usbhid snd_hda_codec hid snd_hwdep snd_pcm microcode snd_page_alloc snd_timer psmouse i2c_algo_bit lpc_ich tpm_tis video wmi mac_hid serio_raw ext2 lp parport r8169 mii
> >>> [  819.771802] CPU: 0 PID: 2167 Comm: bash Not tainted 3.12.0+ #25
> >>> [  819.771876] Hardware name: SAMSUNG ELECTRONICS CO., LTD. 900X3C/900X3D/900X4C/900X4D/SAMSUNG_NP1234567890, BIOS P03AAC 07/12/2012
> >>> [  819.772022] task: ffff88002e6ddcc0 ti: ffff8804015ca000 task.ti: ffff8804015ca000
> >>> [  819.772119] RIP: 0010:[<ffffffff813381c0>]  [<ffffffff813381c0>] skip_spaces+0x30/0x30
> >>> [  819.772242] RSP: 0018:ffff8804015cbc70  EFLAGS: 00010046
> >>> [  819.772310] RAX: 0000000000000003 RBX: ffff88040cfd6d40 RCX: 0000000000000018
> >>> [  819.772397] RDX: 0000000000020001 RSI: 0000000000000000 RDI: 0000000000000000
> >>> [  819.772484] RBP: ffff8804015cbcc0 R08: 0000000000000000 R09: ffff8803f0768d40
> >>> [  819.772570] R10: ffffea001033b800 R11: 0000000000000000 R12: ffffffff81c519c0
> >>> [  819.772656] R13: 0000000000020001 R14: 0000000000000000 R15: 0000000000020001
> >>> [  819.772744] FS:  00007ff98309b740(0000) GS:ffff88041f200000(0000) knlGS:0000000000000000
> >>> [  819.772845] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> [  819.772917] CR2: 0000000000000000 CR3: 00000003f59dc000 CR4: 00000000001407f0
> >>> [  819.773001] Stack:
> >>> [  819.773030]  ffffffff81114003 ffff8804015cbcb0 0000000000000000 0000000000000046
> >>> [  819.773146]  ffff880409757a18 ffff8803f065a160 0000000000000000 0000000000020001
> >>> [  819.773273]  0000000000000000 0000000000000000 ffff8804015cbce8 ffffffff8143e388
> >>> [  819.773387] Call Trace:
> >>> [  819.773434]  [<ffffffff81114003>] ? ftrace_raw_event_wakeup_source+0x43/0xe0
> >>> [  819.773520]  [<ffffffff8143e388>] wakeup_source_report_event+0xb8/0xd0
> >>> [  819.773595]  [<ffffffff8143e3cd>] __pm_stay_awake+0x2d/0x50
> >>> [  819.773724]  [<ffffffff8153395c>] power_supply_changed+0x3c/0x90
> >>> [  819.773795]  [<ffffffff8153407c>] power_supply_register+0x18c/0x250
> >>> [  819.773869]  [<ffffffff813d8d18>] sysfs_add_battery+0x61/0x7b
> >>> [  819.773935]  [<ffffffff813d8d69>] battery_notify+0x37/0x3f
> >>> [  819.774001]  [<ffffffff816ccb7c>] notifier_call_chain+0x4c/0x70
> >>> [  819.774071]  [<ffffffff81073ded>] __blocking_notifier_call_chain+0x4d/0x70
> >>> [  819.774149]  [<ffffffff81073e26>] blocking_notifier_call_chain+0x16/0x20
> >>> [  819.774227]  [<ffffffff8109397a>] pm_notifier_call_chain+0x1a/0x40
> >>> [  819.774316]  [<ffffffff81095b66>] hibernate+0x66/0x1c0
> >>> [  819.774407]  [<ffffffff81093931>] state_store+0x71/0xa0
> >>> [  819.774507]  [<ffffffff81331d8f>] kobj_attr_store+0xf/0x20
> >>> [  819.774613]  [<ffffffff811f8618>] sysfs_write_file+0x128/0x1c0
> >>> [  819.774735]  [<ffffffff8118579d>] vfs_write+0xbd/0x1e0
> >>> [  819.774841]  [<ffffffff811861d9>] SyS_write+0x49/0xa0
> >>> [  819.774939]  [<ffffffff816d1052>] system_call_fastpath+0x16/0x1b
> >>> [  819.775055] Code: 89 f8 48 89 e5 f6 82 c0 a6 84 81 20 74 15 0f 1f 44 00 00 48 83 c0 01 0f b6 10 f6 82 c0 a6 84 81 20 75 f0 5d c3 66 0f 1f 44 00 00 <80> 3f 00 55 48 89 e5 74 15 48 89 f8 0f 1f 40 00 48 83 c0 01 80
> >>> [  819.775760] RIP  [<ffffffff813381c0>] skip_spaces+0x30/0x30
> >>> [  819.775881]  RSP <ffff8804015cbc70>
> >>> [  819.775949] CR2: 0000000000000000
> >>> [  819.794175] ---[ end trace c4ef25127039952e ]---
> >>>
> >>> Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
> >>> ---
> >>>   drivers/base/power/wakeup.c | 3 +++
> >>>   1 file changed, 3 insertions(+)
> >>>
> >>> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> >>> index 2d56f41..a605f0d 100644
> >>> --- a/drivers/base/power/wakeup.c
> >>> +++ b/drivers/base/power/wakeup.c
> >>> @@ -223,6 +223,9 @@ int device_wakeup_enable(struct device *dev)
> >>>   	if (!dev || !dev->power.can_wakeup)
> >>>   		return -EINVAL;
> >>>
> >>> +	if (WARN_ON(!dev_name(dev)))
> >>> +		return -EINVAL;
> >>> +
> >>>   	ws = wakeup_source_register(dev_name(dev));
> >>
> >> Shouldn't wakeup_source_register() just handle a NULL for a name better?
> >
> > In fact, it does.
> >
> > The bug is in wakeup_source_activate() and that's because it passes ws->name
> > to trace_wakeup_source_activate() which then doesn't bother to check it against
> > NULL.
> >
> > So the solution here is to check ws->name before attempting to pass
> > it to trace_wakeup_source_activate() in wakeup_source_activate().  It is
> > actually valid to have a wakeup source with a NULL name and it shouldn't
> > blow up like this.
> >
> > Thanks,
> > Rafael
> >
> 
> Rafael beat me to it. Yes adding the following to 
> DECLARE_EVENT_CLASS(wakeup_source, should take care of the problem:
> 
> 
>                const char *tmp_i = name ? name : "ws no name";
> 
>                  __assign_str(name, tmp_i);
> 
> should make trace_wakeup_source_activate() not blow up. I did consider 
> this as one of the fixes to the oops. Would you rather see this fix 
> instead of this change to device_wakeup_enable()?

No, that's fine, it makes more sense now.

greg k-h