[0/2] Fix truncation warnings from building test_scanf.c

Message

Richard Fitzgerald May 24, 2021, 3:59 p.m. UTC

The kernel test robot is reporting truncation warnings when building
lib/test_scanf.c:

1) lib/test_scanf.c:250:9: sparse: sparse: cast truncates bits from
   constant value (ffff0001 becomes 1)
   Reported on several lines.

2) include/linux/prandom.h:114:45: sparse: sparse: cast truncates bits
   from constant value (4f2e5357408c3c09 becomes 408c3c09)


(1) is caused by test_scanf.c using type_min() on an unsigned type. The
type_min() macro calculates -type_max() - 1, so is only meaningful for
signed types.

(2) is caused by prandom_seed_state() storing a modified u64 seed value
into a u32 - sparse will warn that this causes a truncation. 

The two patches in this series fix these problems.

Richard Fitzgerald (2):
  lib: test_scanf: Fix incorrect use of type_min() with unsigned types
  random32: Fix implicit truncation warning in prandom_seed_state()

 include/linux/prandom.h |  2 +-
 lib/test_scanf.c        | 13 ++++++-------
 2 files changed, 7 insertions(+), 8 deletions(-)

Comments

Petr Mladek May 25, 2021, 9:20 a.m. UTC | #1

On Mon 2021-05-24 16:59:39, Richard Fitzgerald wrote:
> The kernel test robot is reporting truncation warnings when building
> lib/test_scanf.c:
> 
> Richard Fitzgerald (2):
>   lib: test_scanf: Fix incorrect use of type_min() with unsigned types
>   random32: Fix implicit truncation warning in prandom_seed_state()
> 
>  include/linux/prandom.h |  2 +-
>  lib/test_scanf.c        | 13 ++++++-------
>  2 files changed, 7 insertions(+), 8 deletions(-)

For both patches:

Reviewed-by: Petr Mladek <[e-mail]>

I am going to commit them within next two days or so unless anyone
complains in the meantime.

Thanks a lot for fixing it.

Best Regards,
Petr

Petr Mladek May 27, 2021, 2:10 p.m. UTC | #2

On Tue 2021-05-25 11:20:45, Petr Mladek wrote:
> On Mon 2021-05-24 16:59:39, Richard Fitzgerald wrote:
> > The kernel test robot is reporting truncation warnings when building
> > lib/test_scanf.c:
> > 
> > Richard Fitzgerald (2):
> >   lib: test_scanf: Fix incorrect use of type_min() with unsigned types
> >   random32: Fix implicit truncation warning in prandom_seed_state()
> > 
> >  include/linux/prandom.h |  2 +-
> >  lib/test_scanf.c        | 13 ++++++-------
> >  2 files changed, 7 insertions(+), 8 deletions(-)
> 
> For both patches:
> 
> Reviewed-by: Petr Mladek <[e-mail]>
> 
> I am going to commit them within next two days or so unless anyone
> complains in the meantime.

JFYI, both patches have been committed into  printk/linux.git,
branch for-5.14-vsprintf-scanf.

Best Regards,
Petr