Re: [PATCH] timex: Use 64-bit fields on 32-bit TIMESIZE=64 systems

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 14/10/2021 18:17, Stafford Horne via Libc-alpha wrote:
> This was found when testing the OpenRISC port I am working on.  These
> two tests fail with SIGSEGV:
> 
>   FAIL: misc/tst-ntp_gettime
>   FAIL: misc/tst-ntp_gettimex
> 
> This was found to be due to the kernel overwriting the stack space
> allocated by the timex structure.  The reason for the overwrite being
> that the kernel timex has 64-bit fields and user space code only
> allocates enough stack space for timex with 32-bit fields.
> 
> On 32-bit systems with TIMESIZE=64 __USE_TIME_BITS64 is not defined.
> This causes the timex structure to use 32-bit fields with type
> __syscall_slong_t.> 
> This patch adjusts the ifdef condition to allow 32-bit systems with
> TIMESIZE=64 to use the 64-bit long long timex definition.

Why is this not an issue for arc or riscv32? Both are 32-bit architectures
have default 64-bit time_t.

This changes all current 32-bit architectures with default 64-bit time_t
and I not sure if this break something (or if the interface is already
broken).  I will try to check on riscv32.


> ---
>  sysdeps/unix/sysv/linux/bits/timex.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/bits/timex.h b/sysdeps/unix/sysv/linux/bits/timex.h
> index ee37694e8f..4a5db6deca 100644
> --- a/sysdeps/unix/sysv/linux/bits/timex.h
> +++ b/sysdeps/unix/sysv/linux/bits/timex.h
> @@ -25,7 +25,7 @@
>  
>  struct timex
>  {
> -# ifdef __USE_TIME_BITS64
> +# if defined __USE_TIME_BITS64 || (__TIMESIZE == 64 && __WORDSIZE == 32)
>    unsigned int modes;          /* mode selector */
>    int :32;                     /* pad */
>    long long offset;            /* time offset (usec) */
>