Re: [PATCH v3 1/9] bsd-user/mmap.c: Always zero MAP_ANONYMOUS memory in mmap_frag()

[Kyle Evans]

On Fri, Oct 8, 2021 at 4:24 PM Warner Losh <imp@bsdimp.com> wrote:
>
> From: Mikaël Urankar <mikael.urankar@gmail.com>
>
> Similar to the equivalent linux-user commit e6deac9cf99
>
> When mapping MAP_ANONYMOUS memory fragments, still need notice about to
> set it zero, or it will cause issues.
>
> Signed-off-by: Mikaël Urankar <mikael.urankar@gmail.com>
> Signed-off-by: Warner Losh <imp@bsdimp.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  bsd-user/mmap.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/bsd-user/mmap.c b/bsd-user/mmap.c
> index b40ab9045f..fc3c1480f5 100644
> --- a/bsd-user/mmap.c
> +++ b/bsd-user/mmap.c
> @@ -180,10 +180,12 @@ static int mmap_frag(abi_ulong real_start,
>          if (prot_new != (prot1 | PROT_WRITE))
>              mprotect(host_start, qemu_host_page_size, prot_new);
>      } else {
> -        /* just update the protection */
>          if (prot_new != prot1) {
>              mprotect(host_start, qemu_host_page_size, prot_new);
>          }
> +        if (prot_new & PROT_WRITE) {
> +            memset(g2h_untagged(start), 0, end - start);
> +        }
>      }
>      return 0;
>  }
> --
> 2.32.0
>

Reviewed-by: Kyle Evans <kevans@FreeBSD.org>