diff mbox series

[next] block: scsi_ioctl: Avoid the use of one-element arrays

Message ID 20201002231033.GA6273@embeddedor
State New, archived
Headers show
Series [next] block: scsi_ioctl: Avoid the use of one-element arrays | expand

Commit Message

Gustavo A. R. Silva Oct. 2, 2020, 11:10 p.m. UTC
One-element arrays are being deprecated[1]. Replace the one-element array
with a simple object of type compat_caddr_t: 'compat_caddr_t unused'[2],
once it seems this field is actually never used.

Also, update struct cdrom_generic_command in UAPI by adding an
anonimous union to avoid using the one-element array _reserved_.

[1] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
[2] https://github.com/KSPP/linux/issues/86

Build-tested-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/5f76f5d0.qJ4t%2FHWuRzSW7bTa%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 block/scsi_ioctl.c         | 6 +++---
 include/uapi/linux/cdrom.h | 5 ++++-
 2 files changed, 7 insertions(+), 4 deletions(-)

Comments

Jens Axboe Oct. 2, 2020, 11:53 p.m. UTC | #1
On 10/2/20 5:10 PM, Gustavo A. R. Silva wrote:
> diff --git a/include/uapi/linux/cdrom.h b/include/uapi/linux/cdrom.h
> index 2817230148fd..6c34f6e2f1f7 100644
> --- a/include/uapi/linux/cdrom.h
> +++ b/include/uapi/linux/cdrom.h
> @@ -289,7 +289,10 @@ struct cdrom_generic_command
>  	unsigned char		data_direction;
>  	int			quiet;
>  	int			timeout;
> -	void			__user *reserved[1];	/* unused, actually */
> +	union {
> +		void		__user *reserved[1];	/* unused, actually */
> +		void            __user *unused;
> +	};

What's the point of this union, why not just turn it into

	void *			__user *unused;

?
Jens Axboe Oct. 2, 2020, 11:58 p.m. UTC | #2
On 10/2/20 6:03 PM, Gustavo A. R. Silva wrote:
> On Fri, Oct 02, 2020 at 05:53:05PM -0600, Jens Axboe wrote:
>> On 10/2/20 5:10 PM, Gustavo A. R. Silva wrote:
>>> diff --git a/include/uapi/linux/cdrom.h b/include/uapi/linux/cdrom.h
>>> index 2817230148fd..6c34f6e2f1f7 100644
>>> --- a/include/uapi/linux/cdrom.h
>>> +++ b/include/uapi/linux/cdrom.h
>>> @@ -289,7 +289,10 @@ struct cdrom_generic_command
>>>  	unsigned char		data_direction;
>>>  	int			quiet;
>>>  	int			timeout;
>>> -	void			__user *reserved[1];	/* unused, actually */
>>> +	union {
>>> +		void		__user *reserved[1];	/* unused, actually */
>>> +		void            __user *unused;
>>> +	};
>>
>> What's the point of this union, why not just turn it into
>>
>> 	void *			__user *unused;
>>
>> ?
> 
> I just don't want to take any chances of breaking any user-space
> application that, for some reason, may be considering that field.

I guess that's a valid concern, who knows what applications are doing
to an ignored field.

I'll apply it, thanks.
Gustavo A. R. Silva Oct. 3, 2020, 12:03 a.m. UTC | #3
On Fri, Oct 02, 2020 at 05:53:05PM -0600, Jens Axboe wrote:
> On 10/2/20 5:10 PM, Gustavo A. R. Silva wrote:
> > diff --git a/include/uapi/linux/cdrom.h b/include/uapi/linux/cdrom.h
> > index 2817230148fd..6c34f6e2f1f7 100644
> > --- a/include/uapi/linux/cdrom.h
> > +++ b/include/uapi/linux/cdrom.h
> > @@ -289,7 +289,10 @@ struct cdrom_generic_command
> >  	unsigned char		data_direction;
> >  	int			quiet;
> >  	int			timeout;
> > -	void			__user *reserved[1];	/* unused, actually */
> > +	union {
> > +		void		__user *reserved[1];	/* unused, actually */
> > +		void            __user *unused;
> > +	};
> 
> What's the point of this union, why not just turn it into
> 
> 	void *			__user *unused;
> 
> ?

I just don't want to take any chances of breaking any user-space
application that, for some reason, may be considering that field.

--
Gustavo
Gustavo A. R. Silva Oct. 3, 2020, 12:07 a.m. UTC | #4
On Fri, Oct 02, 2020 at 05:58:33PM -0600, Jens Axboe wrote:
> >>> -	void			__user *reserved[1];	/* unused, actually */
> >>> +	union {
> >>> +		void		__user *reserved[1];	/* unused, actually */
> >>> +		void            __user *unused;
> >>> +	};
> >>
> >> What's the point of this union, why not just turn it into
> >>
> >> 	void *			__user *unused;
> >>
> >> ?
> > 
> > I just don't want to take any chances of breaking any user-space
> > application that, for some reason, may be considering that field.
> 
> I guess that's a valid concern, who knows what applications are doing
> to an ignored field.
> 
> I'll apply it, thanks.

Awesome. :)

Thanks.
--
Gustavo
Christoph Hellwig Oct. 5, 2020, 7:25 a.m. UTC | #5
On Fri, Oct 02, 2020 at 06:10:33PM -0500, Gustavo A. R. Silva wrote:
> One-element arrays are being deprecated[1]. Replace the one-element array
> with a simple object of type compat_caddr_t: 'compat_caddr_t unused'[2],
> once it seems this field is actually never used.

They are only deprecated when abused as variable length array.  That is
not the case here.
diff mbox series

Patch

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 600e38cb69b2..2dfb699389df 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -643,7 +643,7 @@  struct compat_cdrom_generic_command {
 	unsigned char	data_direction;
 	compat_int_t	quiet;
 	compat_int_t	timeout;
-	compat_caddr_t	reserved[1];
+	compat_caddr_t	unused;
 };
 #endif
 
@@ -665,7 +665,7 @@  static int scsi_get_cdrom_generic_arg(struct cdrom_generic_command *cgc,
 			.data_direction	= cgc32.data_direction,
 			.quiet		= cgc32.quiet,
 			.timeout	= cgc32.timeout,
-			.reserved[0]	= compat_ptr(cgc32.reserved[0]),
+			.unused		= compat_ptr(cgc32.unused),
 		};
 		memcpy(&cgc->cmd, &cgc32.cmd, CDROM_PACKET_SIZE);
 		return 0;
@@ -690,7 +690,7 @@  static int scsi_put_cdrom_generic_arg(const struct cdrom_generic_command *cgc,
 			.data_direction	= cgc->data_direction,
 			.quiet		= cgc->quiet,
 			.timeout	= cgc->timeout,
-			.reserved[0]	= (uintptr_t)(cgc->reserved[0]),
+			.unused		= (uintptr_t)(cgc->unused),
 		};
 		memcpy(&cgc32.cmd, &cgc->cmd, CDROM_PACKET_SIZE);
 
diff --git a/include/uapi/linux/cdrom.h b/include/uapi/linux/cdrom.h
index 2817230148fd..6c34f6e2f1f7 100644
--- a/include/uapi/linux/cdrom.h
+++ b/include/uapi/linux/cdrom.h
@@ -289,7 +289,10 @@  struct cdrom_generic_command
 	unsigned char		data_direction;
 	int			quiet;
 	int			timeout;
-	void			__user *reserved[1];	/* unused, actually */
+	union {
+		void		__user *reserved[1];	/* unused, actually */
+		void            __user *unused;
+	};
 };
 
 /*