Re: [PATCH v2 02/11] linux-user: Fix the execfd case of /proc/self/exe open

[Laurent Vivier <laurent@vivier.eu>]

Le 31/05/2021 à 07:50, YAMAMOTO Takashi a écrit :
> It's problematic to return AT_EXECFD as it is because the user app
> would close it.
> This patch opens it via /proc/self/fd instead.
> 
> Signed-off-by: YAMAMOTO Takashi <yamamoto@midokura.com>
> ---
>  linux-user/syscall.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index a2b03ecb8b..14a63518e2 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -8118,7 +8118,17 @@ static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags,
>  
>      if (is_proc_myself(pathname, "exe")) {
>          int execfd = qemu_getauxval(AT_EXECFD);
> -        return execfd ? execfd : safe_openat(dirfd, exec_path, flags, mode);
> +        if (execfd) {
> +            char filename[PATH_MAX];
> +            int ret;
> +
> +            snprintf(filename, sizeof(filename), "/proc/self/fd/%d", execfd);
> +            ret = safe_openat(dirfd, filename, flags, mode);
> +            if (ret != -1) {
> +                return ret;
> +            }
> +        }
> +        return safe_openat(dirfd, exec_path, flags, mode);
>      }
>  
>      for (fake_open = fakes; fake_open->filename; fake_open++) {
> 

I think a dup() would be more appropriate, or explain why not.

Thanks,
Laurent