linux-next: build warning after merge of the pstore tree

linux-next: build warning after merge of the pstore tree

[Stephen Rothwell]

Hi Kees,

After merging the pstore tree, today's linux-next build (x86_64
allmodconfig) produced this warning:

In file included from include/linux/rcupdate.h:38:0,
                 from include/linux/idr.h:18,
                 from include/linux/kernfs.h:14,
                 from include/linux/sysfs.h:15,
                 from include/linux/kobject.h:21,
                 from include/linux/device.h:17,
                 from fs/pstore/ram_core.c:17:
fs/pstore/ram_core.c: In function 'buffer_size_add':
include/linux/spinlock.h:246:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
   _raw_spin_unlock_irqrestore(lock, flags); \
   ^
fs/pstore/ram_core.c:78:16: note: 'flags' was declared here
  unsigned long flags;
                ^
In file included from include/linux/rcupdate.h:38:0,
                 from include/linux/idr.h:18,
                 from include/linux/kernfs.h:14,
                 from include/linux/sysfs.h:15,
                 from include/linux/kobject.h:21,
                 from include/linux/device.h:17,
                 from fs/pstore/ram_core.c:17:
fs/pstore/ram_core.c: In function 'buffer_start_add':
include/linux/spinlock.h:246:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
   _raw_spin_unlock_irqrestore(lock, flags); \
   ^
fs/pstore/ram_core.c:56:16: note: 'flags' was declared here
  unsigned long flags;
                ^

Introduced by commit

  95937ddce59a ("pstore: Allow prz to control need for locking")

They appear to be a very noisy false positives. :-(

-- 
Cheers,
Stephen Rothwell

Re: linux-next: build warning after merge of the pstore tree

[Kees Cook]

On Tue, Nov 15, 2016 at 4:27 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> Hi Kees,
>
> After merging the pstore tree, today's linux-next build (x86_64
> allmodconfig) produced this warning:
>
> In file included from include/linux/rcupdate.h:38:0,
>                  from include/linux/idr.h:18,
>                  from include/linux/kernfs.h:14,
>                  from include/linux/sysfs.h:15,
>                  from include/linux/kobject.h:21,
>                  from include/linux/device.h:17,
>                  from fs/pstore/ram_core.c:17:
> fs/pstore/ram_core.c: In function 'buffer_size_add':
> include/linux/spinlock.h:246:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
>    _raw_spin_unlock_irqrestore(lock, flags); \
>    ^
> fs/pstore/ram_core.c:78:16: note: 'flags' was declared here
>   unsigned long flags;
>                 ^
> In file included from include/linux/rcupdate.h:38:0,
>                  from include/linux/idr.h:18,
>                  from include/linux/kernfs.h:14,
>                  from include/linux/sysfs.h:15,
>                  from include/linux/kobject.h:21,
>                  from include/linux/device.h:17,
>                  from fs/pstore/ram_core.c:17:
> fs/pstore/ram_core.c: In function 'buffer_start_add':
> include/linux/spinlock.h:246:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
>    _raw_spin_unlock_irqrestore(lock, flags); \
>    ^
> fs/pstore/ram_core.c:56:16: note: 'flags' was declared here
>   unsigned long flags;
>                 ^
>
> Introduced by commit
>
>   95937ddce59a ("pstore: Allow prz to control need for locking")
>
> They appear to be a very noisy false positives. :-(

Hah. Ironically, I ran sparse against this code to make sure it would
be happy with the conditional locking, and totally missed the flags
bit. I'll switch it to explicitly initialize flags to silence this.

Thanks!

-Kees

-- 
Kees Cook
Nexus Security

Re: linux-next: build warning after merge of the pstore tree

[Joel Fernandes]

On Tue, Nov 15, 2016 at 4:35 PM, Kees Cook <keescook@chromium.org> wrote:
> On Tue, Nov 15, 2016 at 4:27 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>> Hi Kees,
>>
>> After merging the pstore tree, today's linux-next build (x86_64
>> allmodconfig) produced this warning:
>>
>> In file included from include/linux/rcupdate.h:38:0,
>>                  from include/linux/idr.h:18,
>>                  from include/linux/kernfs.h:14,
>>                  from include/linux/sysfs.h:15,
>>                  from include/linux/kobject.h:21,
>>                  from include/linux/device.h:17,
>>                  from fs/pstore/ram_core.c:17:
>> fs/pstore/ram_core.c: In function 'buffer_size_add':
>> include/linux/spinlock.h:246:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
>>    _raw_spin_unlock_irqrestore(lock, flags); \
>>    ^
>> fs/pstore/ram_core.c:78:16: note: 'flags' was declared here
>>   unsigned long flags;
>>                 ^
>> In file included from include/linux/rcupdate.h:38:0,
>>                  from include/linux/idr.h:18,
>>                  from include/linux/kernfs.h:14,
>>                  from include/linux/sysfs.h:15,
>>                  from include/linux/kobject.h:21,
>>                  from include/linux/device.h:17,
>>                  from fs/pstore/ram_core.c:17:
>> fs/pstore/ram_core.c: In function 'buffer_start_add':
>> include/linux/spinlock.h:246:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
>>    _raw_spin_unlock_irqrestore(lock, flags); \
>>    ^
>> fs/pstore/ram_core.c:56:16: note: 'flags' was declared here
>>   unsigned long flags;
>>                 ^
>>
>> Introduced by commit
>>
>>   95937ddce59a ("pstore: Allow prz to control need for locking")
>>
>> They appear to be a very noisy false positives. :-(
>
> Hah. Ironically, I ran sparse against this code to make sure it would
> be happy with the conditional locking, and totally missed the flags
> bit. I'll switch it to explicitly initialize flags to silence this.
>

Ah! False positive.

Thanks a lot Kees for fixing it.

Regards,
Joel

linux-next: build warning after merge of the pstore tree

[Stephen Rothwell]

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Hi all,

After merging the pstore tree, today's linux-next build (htmldocs)
produced this warning:

fs/pstore/blk.c:1: warning: no structured comments found

Introduced by commit

  38c18fec13fb ("pstore/blk: Use the normal block device I/O path")

The last kernedoc comment in this file is removed by this commit.

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: build warning after merge of the pstore tree

[Kees Cook]

On Tue, Jun 15, 2021 at 08:15:16PM +1000, Stephen Rothwell wrote:
> Hi all,
> 
> After merging the pstore tree, today's linux-next build (htmldocs)
> produced this warning:
> 
> fs/pstore/blk.c:1: warning: no structured comments found
> 
> Introduced by commit
> 
>   38c18fec13fb ("pstore/blk: Use the normal block device I/O path")
> 
> The last kernedoc comment in this file is removed by this commit.

I was briefly quite confused by this. I see now it's the
:internal: not the :export: use of blk.c. If it's possible to
improve this error report email with more details in the future,
that would be nice. For example, "blk.c:1" isn't helpful, but
"Documentation/admin-guide/pstore-blk.rst:230" would be. :)

I'll get this fixed up; thanks!

-Kees

-- 
Kees Cook