Re: [PATCH v3 2/2] tracing: Fix Oops from NULL pointer dereference from __assign_str

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On Fri, 22 Nov 2013 23:18:09 +0100
"Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> wrote:

> On Friday, November 22, 2013 10:54:29 AM Shuah Khan wrote:
> > Tracing infrastructure routine __assign_str doesn't handle null strings.
> > As a result when an trace event passes in a null string, kernel panics
> > when skip_spaces() is invoked on the string. The following oops occurred
> > when a null wakeup source name is specified.
> > 
> > power_supply_register() calls device_init_wakeup() to register a wakeup
> > source before initializing dev_name. As a result, device_wakeup_enable()
> > end up registering wakeup source with a null name when wakeup_source_register()
> > gets called with dev_name(dev) which is null at the time.
> > 
> > When kernel is booted with wakeup_source_activate enabled, it will panic
> > when the trace point code tries to dereference ws->name. Registering a
> > a wakeup source without a name should be possible.
> > 
> > Fix tracing infrastructure to be more robust in handling null strings in
> > __assign_string() and __string(). With this change null string is handled
> > gracefully and replacing it with "(null)" when trace is generated. This will
> > address the problem at the tracing infrastructure level which is better than
> > fixing individual tracepoint code.
> > 
> > Trace after the fix:
> >             bash-2177  [000] d...   583.560106: wakeup_source_activate: (null) state=0x20001
> >      kworker/0:2-378   [000] d...   583.560714: wakeup_source_deactivate: (null) state=0x30000
> > 
> > Oops message:
> > 
> > [  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@xxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> 
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

The below is my patch. I have it in my queue and I will be pushing it
after it succeeds all my testing.

-- Steve

> 
> > ---
> >  include/trace/ftrace.h | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> > index 52594b2..79f4639 100644
> > --- a/include/trace/ftrace.h
> > +++ b/include/trace/ftrace.h
> > @@ -372,7 +372,9 @@ ftrace_define_fields_##call(struct ftrace_event_call *event_call)	\
> >  	__data_size += (len) * sizeof(type);
> >  
> >  #undef __string
> > -#define __string(item, src) __dynamic_array(char, item, strlen(src) + 1)
> > +#define __string(item, src)						\
> > +	__dynamic_array(char, item,					\
> > +	   strlen((const char *)src ? (const char *)src : "(null)") + 1)
> >  
> >  #undef DECLARE_EVENT_CLASS
> >  #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)	\
> > @@ -501,7 +503,8 @@ static inline notrace int ftrace_get_offsets_##call(			\
> >  
> >  #undef __assign_str
> >  #define __assign_str(dst, src)						\
> > -	strcpy(__get_str(dst), src);
> > +	strcpy(__get_str(dst),						\
> > +		((const char *)src ? (const char *)src : "(null)"))
> >  
> >  #undef TP_fast_assign
> >  #define TP_fast_assign(args...) args
> > 

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