Re: [PATCH] Increase judgment on buf.

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

On 19/05/23 00:57, Peng Fan wrote:
> When buf is empty, if it is not checked, the subsequent assignment
> operation will trigger a page fault. This is unnecessary.
> 
> Signed-off-by: lixing <lixing@loongson.cn>
> Signed-off-by: Peng Fan <fanpeng@loongson.cn>

The stat family is explicitly marked with nonnull for the input struct
stat buffer, and calling with a NULL argument is an UB.

> ---
>  sysdeps/unix/sysv/linux/fstatat64.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/fstatat64.c b/sysdeps/unix/sysv/linux/fstatat64.c
> index 3509d3ca6d..b635a8299a 100644
> --- a/sysdeps/unix/sysv/linux/fstatat64.c
> +++ b/sysdeps/unix/sysv/linux/fstatat64.c
> @@ -52,9 +52,13 @@ fstatat64_time64_statx (int fd, const char *file, struct __stat64_t64 *buf,
>  {
>    /* 32-bit kABI with default 64-bit time_t, e.g. arc, riscv32.   Also
>       64-bit time_t support is done through statx syscall.  */
> -  struct statx tmp;
> +  struct statx tmp, *ptr;
> +  if (buf)
> +	ptr = &tmp;
> +  else
> +	ptr = NULL;
>    int r = INTERNAL_SYSCALL_CALL (statx, fd, file, AT_NO_AUTOMOUNT | flag,
> -				 STATX_BASIC_STATS, &tmp);
> +				 STATX_BASIC_STATS, ptr);
>    if (r != 0)
>      return r;
>