[PATCH] Linux: Do not check unused bytes after sched_getattr in tst-sched_setattr

[Xi Ruoyao]

On Mon, 2025-01-20 at 10:50 +0100, Florian Weimer wrote:
> Linux 6.13 was released with a change that overwrites those bytes.
> This means that the check_unused subtest fails.
> 
> Update the manual accordingly.
> 
> Tested on x86_64-linux-gnu (although not with Linux 6.13).

Tested on x86_64-linux-gnu with 6.13.

Tested-by: Xi Ruoyao <xry111@xry111.site>

> 
> ---
>  manual/resource.texi                        |  6 +++---
>  sysdeps/unix/sysv/linux/tst-sched_setattr.c | 11 -----------
>  2 files changed, 3 insertions(+), 14 deletions(-)
> 
> diff --git a/manual/resource.texi b/manual/resource.texi
> index 612520d4d9..0b82446817 100644
> --- a/manual/resource.texi
> +++ b/manual/resource.texi
> @@ -1058,9 +1058,9 @@ available in the future.
>  
>  Upon success, @code{@var{attr}->size} contains the size of the structure
>  version used by the kernel.  Fields with offsets greater or equal to
> -@code{@var{attr}->size} are not updated by the kernel.  To obtain
> -predictable values for unknown fields, use @code{memset} to set
> -all @var{size} bytes to zero prior to calling @code{sched_getattr}.
> +@code{@var{attr}->size} may not be overwritten by the kernel.  To obtain
> +predictable values for unknown fields, use @code{memset} to set all
> +@var{size} bytes to zero prior to calling @code{sched_getattr}.
>  
>  On failure, @code{sched_getattr} returns @math{-1} and sets @code{errno}.
>  If @code{errno} is @code{E2BIG}, this means that the buffer is not large
> diff --git a/sysdeps/unix/sysv/linux/tst-sched_setattr.c b/sysdeps/unix/sysv/linux/tst-sched_setattr.c
> index ebad0ae2a8..bf8d9afd34 100644
> --- a/sysdeps/unix/sysv/linux/tst-sched_setattr.c
> +++ b/sysdeps/unix/sysv/linux/tst-sched_setattr.c
> @@ -33,14 +33,6 @@ union
>    unsigned char padding[4096];
>  } u;
>  
> -static void
> -check_unused (void)
> -{
> -  TEST_VERIFY (u.attr.size < sizeof (u));
> -  for (unsigned int i = u.attr.size; i < sizeof (u); ++i)
> -    TEST_COMPARE (u.padding[i], 0xcc);
> -}
> -
>  static int
>  do_test (void)
>  {
> @@ -53,7 +45,6 @@ do_test (void)
>    /* Compiler barrier to bypass write access attribute.  */
>    volatile unsigned int size = sizeof (u);
>    TEST_COMPARE (sched_getattr (0, (struct sched_attr *) &u, size, 0), 0);
> -  check_unused ();
>    TEST_COMPARE (sched_setattr (0, &u.attr, 0), 0); /* Apply unchanged.  */
>  
>    /* Try to switch to the SCHED_OTHER policy.   */
> @@ -81,14 +72,12 @@ do_test (void)
>    memset (&u, 0xcc, sizeof (u));
>    TEST_COMPARE (sched_getattr (0, (struct sched_attr *) &u, size, 0), 0);
>    TEST_COMPARE (u.attr.sched_policy, SCHED_OTHER);
> -  check_unused ();
>  
>    /* Raise the niceless level to 19 and observe its effect.  */
>    TEST_COMPARE (nice (19), 19);
>    TEST_COMPARE (sched_getattr (0, &u.attr, sizeof (u.attr), 0), 0);
>    TEST_COMPARE (u.attr.sched_policy, SCHED_OTHER);
>    TEST_COMPARE (u.attr.sched_nice, 19);
> -  check_unused ();
>  
>    /* Invalid buffer arguments result in EINVAL (not EFAULT).  */
>    {
> 
> base-commit: 8ef17919509e909746b0ad6465e9c6c952a3fe34
> 

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University