linux-kernel - Re: [PATCH 5/6] fs: define a string representation of the kernel_read_file

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Message-ID: <CAGXu5jJ33XUJ+8hvWPg4sKJ6ajqkXU5FeCsuQWuNohvpEHhWWA@mail.gmail.com>
Date:	Thu, 21 Apr 2016 09:47:46 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	James Morris <jmorris@...ei.org>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Joe Perches <joe@...ches.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Jonathan Corbet <corbet@....net>,
	Kalle Valo <kvalo@...eaurora.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Jiri Slaby <jslaby@...e.com>, Paul Moore <pmoore@...hat.com>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Andreas Gruenbacher <agruenba@...hat.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 5/6] fs: define a string representation of the
 kernel_read_file_id enumeration

On Thu, Apr 21, 2016 at 6:26 AM, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> On Wed, 2016-04-20 at 15:46 -0700, Kees Cook wrote:
>> From: Mimi Zohar <zohar@...ux.vnet.ibm.com>
>>
>> A string representation of the kernel_read_file_id enumeration is
>> needed for displaying messages (eg. pr_info, auditing) that can be
>> used by multiple LSMs and the integrity subsystem.  To simplify
>> keeping the list of strings up to date with the enumeration, this
>> patch defines two new preprocessing macros named __fid_enumify and
>> __fid_stringify to create the enumeration and an array of strings.
>> kernel_read_file_id_str() returns a string based on the enumeration.
>>
>> Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
>> [kees: removed removal of my old version, constified pointer values]
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>
>
> I got this
>
> In file included from /home/andy/prj/linux-
> topic/include/linux/seq_file.h:10:0,
>                  from /home/andy/prj/linux-
> topic/include/linux/pinctrl/consumer.h:17,
>                  from /home/andy/prj/linux-
> topic/include/linux/pinctrl/devinfo.h:21,
>                  from /home/andy/prj/linux-
> topic/include/linux/device.h:24,
>                  from /home/andy/prj/linux-
> topic/include/linux/dmaengine.h:20,
>                  from /home/andy/prj/linux-
> topic/drivers/dma/dw/core.c:15:
> /home/andy/prj/linux-topic/include/linux/fs.h:2627:74: warning: type
> qualifiers ignored on function return type [-Wignored-qualifiers]
>  static inline const char * const kernel_read_file_id_str(enum
> kernel_read_file_id id)

What gcc version are you using? Seems like I need to drop the added
"const" on the return?

-Kees

>
>> ---
>>  include/linux/fs.h | 31 +++++++++++++++++++++++++------
>>  1 file changed, 25 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 70e61b58baaf..518716b4834e 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -2590,15 +2590,34 @@ static inline void i_readcount_inc(struct
>> inode *inode)
>>  #endif
>>  extern int do_pipe_flags(int *, int);
>>
>> +#define __kernel_read_file_id(id) \
>> +     id(UNKNOWN, unknown)            \
>> +     id(FIRMWARE, firmware)          \
>> +     id(MODULE, kernel-module)               \
>> +     id(KEXEC_IMAGE, kexec-image)            \
>> +     id(KEXEC_INITRAMFS, kexec-initramfs)    \
>> +     id(POLICY, security-policy)             \
>> +     id(MAX_ID, )
>> +
>> +#define __fid_enumify(ENUM, dummy) READING_ ## ENUM,
>> +#define __fid_stringify(dummy, str) #str,
>> +
>>  enum kernel_read_file_id {
>> -     READING_FIRMWARE = 1,
>> -     READING_MODULE,
>> -     READING_KEXEC_IMAGE,
>> -     READING_KEXEC_INITRAMFS,
>> -     READING_POLICY,
>> -     READING_MAX_ID
>> +     __kernel_read_file_id(__fid_enumify)
>> +};
>> +
>> +static const char * const kernel_read_file_str[] = {
>> +     __kernel_read_file_id(__fid_stringify)
>>  };
>>
>> +static inline const char * const kernel_read_file_id_str(enum
>> kernel_read_file_id id)
>> +{
>> +     if (id < 0 || id >= READING_MAX_ID)
>> +             return kernel_read_file_str[READING_UNKNOWN];
>> +
>> +     return kernel_read_file_str[id];
>> +}
>> +
>>  extern int kernel_read(struct file *, loff_t, char *, unsigned long);
>>  extern int kernel_read_file(struct file *, void **, loff_t *, loff_t,
>>                           enum kernel_read_file_id);
>
> --
> Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Intel Finland Oy
>



-- 
Kees Cook
Chrome OS & Brillo Security