[PATCH v1] posix: Only check shm_unlink obj_err if necessary

[Gedare Bloom]

This looks fine to push to 5.1. I can't test/push it at the moment,
but if someone else can, it would be good to apply. We also need to
apply the other version to master.

On Sat, Jun 27, 2020 at 6:22 PM Kinsey Moore <kinsey.moore at oarcorp.com> wrote:
>
> In the nominal case checked by spsysinit01, obj_err is unmodified if
> _POSIX_Shm_Get_by_name returns non-NULL. In the case of shm_unlink, this means
> an uninitialized value is passed into the switch and it appears tests using it
> were passing by virtue of the stack having the right value on it in most cases.
> This now checks obj_err only if _POSIX_Shm_Get_by_name returns NULL.
>
> Close #4016
> ---
>  cpukit/posix/src/shmunlink.c | 45 ++++++++++++++++++------------------
>  1 file changed, 23 insertions(+), 22 deletions(-)
>
> diff --git a/cpukit/posix/src/shmunlink.c b/cpukit/posix/src/shmunlink.c
> index 053b9c4946..a889b4029c 100644
> --- a/cpukit/posix/src/shmunlink.c
> +++ b/cpukit/posix/src/shmunlink.c
> @@ -29,28 +29,29 @@ int shm_unlink( const char *name )
>    _Objects_Allocator_lock();
>
>    shm = _POSIX_Shm_Get_by_name( name, 0, &obj_err );
> -  switch ( obj_err ) {
> -    case OBJECTS_GET_BY_NAME_INVALID_NAME:
> -      err = ENOENT;
> -      break;
> -
> -    case OBJECTS_GET_BY_NAME_NAME_TOO_LONG:
> -      err = ENAMETOOLONG;
> -      break;
> -
> -    case OBJECTS_GET_BY_NAME_NO_OBJECT:
> -    default:
> -      _Objects_Namespace_remove_string(
> -        &_POSIX_Shm_Information,
> -        &shm->Object
> -      );
> -
> -      if ( shm->reference_count == 0 ) {
> -        /* Only remove the shm object if no references exist to it. Otherwise,
> -         * the shm object will be freed later in _POSIX_Shm_Attempt_delete */
> -        _POSIX_Shm_Free( shm );
> -      }
> -      break;
> +  if ( shm ) {
> +    _Objects_Namespace_remove_string(
> +      &_POSIX_Shm_Information,
> +      &shm->Object
> +    );
> +
> +    if ( shm->reference_count == 0 ) {
> +      /* Only remove the shm object if no references exist to it. Otherwise,
> +       * the shm object will be freed later in _POSIX_Shm_Attempt_delete */
> +      _POSIX_Shm_Free( shm );
> +    }
> +  } else {
> +    switch ( obj_err ) {
> +      case OBJECTS_GET_BY_NAME_NAME_TOO_LONG:
> +        err = ENAMETOOLONG;
> +        break;
> +
> +      case OBJECTS_GET_BY_NAME_INVALID_NAME:
> +      case OBJECTS_GET_BY_NAME_NO_OBJECT:
> +      default:
> +        err = ENOENT;
> +        break;
> +    }
>    }
>
>    _Objects_Allocator_unlock();
> --
> 2.20.1
>
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