When a character array without a terminating NUL character has a static
initializer, GCC 15's -Wunterminated-string-initialization will only
warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
with __nonstring to and correctly identify the char array as "not a C
string" and thereby eliminate the warning.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
Cc: Jack Wang <jinpu.wang@cloud.ionos.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
---
 drivers/scsi/pm8001/pm8001_ctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/pm8001/pm8001_ctl.c b/drivers/scsi/pm8001/pm8001_ctl.c
index 85ff95c6543a..7618f9cc9986 100644
--- a/drivers/scsi/pm8001/pm8001_ctl.c
+++ b/drivers/scsi/pm8001/pm8001_ctl.c
@@ -644,7 +644,7 @@ static DEVICE_ATTR(gsm_log, S_IRUGO, pm8001_ctl_gsm_log_show, NULL);
 #define FLASH_CMD_SET_NVMD    0x02
 
 struct flash_command {
-     u8      command[8];
+     u8      command[8] __nonstring;
      int     code;
 };
 
-- 
2.34.1

On Mon, 2025-03-10 at 15:25 -0700, Kees Cook wrote:
> When a character array without a terminating NUL character has a
> static
> initializer, GCC 15's -Wunterminated-string-initialization will only
> warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
> with __nonstring to and correctly identify the char array as "not a C
> string" and thereby eliminate the warning.
> 
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
> Cc: Jack Wang <jinpu.wang@cloud.ionos.com>
> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
> Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
> Cc: linux-scsi@vger.kernel.org
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
>  drivers/scsi/pm8001/pm8001_ctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/pm8001/pm8001_ctl.c
> b/drivers/scsi/pm8001/pm8001_ctl.c
> index 85ff95c6543a..7618f9cc9986 100644
> --- a/drivers/scsi/pm8001/pm8001_ctl.c
> +++ b/drivers/scsi/pm8001/pm8001_ctl.c
> @@ -644,7 +644,7 @@ static DEVICE_ATTR(gsm_log, S_IRUGO,
> pm8001_ctl_gsm_log_show, NULL);
>  #define FLASH_CMD_SET_NVMD    0x02
>  
>  struct flash_command {
> -     u8      command[8];
> +     u8      command[8] __nonstring;

This looks a bit suboptimal ... is there anywhere in the kernel u8[] is
actually used for real strings?  In which case it would seem the better
place to put the annotation is in the typedef for u8 arrays.

Regards,

James

On Mon, Mar 10, 2025 at 06:38:01PM -0400, James Bottomley wrote:
> On Mon, 2025-03-10 at 15:25 -0700, Kees Cook wrote:
> > When a character array without a terminating NUL character has a
> > static
> > initializer, GCC 15's -Wunterminated-string-initialization will only
> > warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
> > with __nonstring to and correctly identify the char array as "not a C
> > string" and thereby eliminate the warning.
> > 
> > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
> > Cc: Jack Wang <jinpu.wang@cloud.ionos.com>
> > Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
> > Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
> > Cc: linux-scsi@vger.kernel.org
> > Signed-off-by: Kees Cook <kees@kernel.org>
> > ---
> >  drivers/scsi/pm8001/pm8001_ctl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/scsi/pm8001/pm8001_ctl.c
> > b/drivers/scsi/pm8001/pm8001_ctl.c
> > index 85ff95c6543a..7618f9cc9986 100644
> > --- a/drivers/scsi/pm8001/pm8001_ctl.c
> > +++ b/drivers/scsi/pm8001/pm8001_ctl.c
> > @@ -644,7 +644,7 @@ static DEVICE_ATTR(gsm_log, S_IRUGO,
> > pm8001_ctl_gsm_log_show, NULL);
> >  #define FLASH_CMD_SET_NVMD    0x02
> >  
> >  struct flash_command {
> > -     u8      command[8];
> > +     u8      command[8] __nonstring;
> 
> This looks a bit suboptimal ... is there anywhere in the kernel u8[] is
> actually used for real strings?  In which case it would seem the better
> place to put the annotation is in the typedef for u8 arrays.

I answered this in a merged thread[1]. Can this get picked up?

Thanks!

-Kees

[1] https://lore.kernel.org/lkml/202503111520.CF7527A@keescook/

-- 
Kees Cook

Kees,

>> > When a character array without a terminating NUL character has a
>> > static initializer, GCC 15's -Wunterminated-string-initialization
>> > will only warn if the array lacks the "nonstring" attribute[1].
>> > Mark the arrays with __nonstring to and correctly identify the char
>> > array as "not a C string" and thereby eliminate the warning.

Applied to 6.16/scsi-staging, thanks!

-- 
Martin K. Petersen