| Message ID | 20201002231033.GA6273@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [next] block: scsi_ioctl: Avoid the use of one-element arrays | expand |
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; ?
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.
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
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
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 --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; + }; }; /*
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(-)