Made sure when running as the effective user root (euid is zero) we actually become

uid 0 in order to avoid file system permission errors/restrictions.

doas.c

@@ -526,6 +526,11 @@ main(int argc, char **argv)
         dup2(temp_stdout, 1);
         #endif
 
+        /* If we effectively root, set the UID to actually be root to avoid
+           permission errors. */
+        if ( geteuid() == ROOT_UID )
+           setuid(ROOT_UID);
+
 	syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s",
 	    myname, cmdline, pw->pw_name, cwd);
 

doas.h

@@ -31,6 +31,10 @@ char **prepenv(struct rule *);
 #define GID_MAX 65535
 #endif
 
+#ifndef ROOT_UID
+#define ROOT_UID 0
+#endif
+
 #ifndef _PW_NAME_LEN
 #define _PW_NAME_LEN 32
 #endif