Re: [Xen-devel] [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Peter Maydell <peter.maydell@xxxxxxxxxx>]

On 4 October 2017 at 17:18, Ian Jackson <ian.jackson@xxxxxxxxxxxxx> wrote:
> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
>
> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> ---


> @@ -166,17 +187,19 @@ void os_parse_cmd_args(int index, const char *optarg)
>
>  static void change_process_uid(void)
>  {
> -    if (user_pwd) {
> -        if (setgid(user_pwd->pw_gid) < 0) {
> +    if (user_pwd || user_uid != (uid_t)-1) {
> +        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
>              fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);

If you're changing the gid we pass to setgid() I think you should
also change the value we tell the user we tried to use in the
error message, or it could be rather confusing.

>              exit(1);
>          }
> -        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> +        if ((user_pwd
> +             ? initgroups(user_pwd->pw_name, user_pwd->pw_gid)
> +             : setgroups(1, &user_gid)) < 0) {
>              fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
>                      user_pwd->pw_name, user_pwd->pw_gid);

...and here we might claim we failed initgroups() when we actually
failed setgroups().

>              exit(1);
>          }
> -        if (setuid(user_pwd->pw_uid) < 0) {
> +        if (setuid(user_pwd ? user_pwd->pw_uid : user_gid) < 0) {
>              fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);

This error message should be updated too.

thanks
-- PMM

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