xargs: improve foundeof check for -E

[yuripv]

Summary

PR: 270867

4aeb63826e0f got it almost correct (we can't use strcmp() here as
current argument isn't guaranteed to be NUL-terminated), but we also
need to check that current argument length is equal to that of eofstr.

usr.bin/xargs/xargs.c

 static int
 tzloadbody(char const *name, struct state *sp, bool doextend,
            union local_storage *lsp)
 {
         register int                    i;
         register int                    fid;
         register int                    stored;
         register ssize_t                nread;
-        register bool doaccess;
         register union input_buffer *up = &lsp->u.u;
         register int tzheadsize = sizeof(struct tzhead);
 
         sp->goback = sp->goahead = false;
 
         if (! name) {
                 name = TZDEFAULT;
                 if (! name)
                   return EINVAL;
         }
 
         if (name[0] == ':')
                 ++name;
-#ifdef SUPPRESS_TZDIR
-        /* Do not prepend TZDIR.  This is intended for specialized
-           applications only, due to its security implications.  */
-        doaccess = true;
-#else
-        doaccess = name[0] == '/';
-#endif
-        if (!doaccess) {
-                char const *dot;
+        if (name[0] != '/') {
                 if (sizeof lsp->fullname - sizeof tzdirslash <= strlen(name))
                   return ENAMETOOLONG;
 
                 /* Create a string "TZDIR/NAME".  Using sprintf here
                    would pull in stdio (and would fail if the
                    resulting string length exceeded INT_MAX!).  */
                 memcpy(lsp->fullname, tzdirslash, sizeof tzdirslash);
                 strcpy(lsp->fullname + sizeof tzdirslash, name);
 
-                /* Set doaccess if NAME contains a ".." file name
-                   component, as such a name could read a file outside
-                   the TZDIR virtual subtree.  */
-                for (dot = name; (dot = strchr(dot, '.')); dot++)
-                  if ((dot == name || dot[-1] == '/') && dot[1] == '.'
-                      && (dot[2] == '/' || !dot[2])) {
-                    doaccess = true;
-                    break;
-                  }
-
                 name = lsp->fullname;
         }
-        if (doaccess && access(name, R_OK) != 0)
-          return errno;
         if (doextend) {
                 /*
                  * Detect if the timezone file has changed.  Check
                  * 'doextend' to ignore TZDEFRULES; the change_in_tz()
                  * function can only keep state for a single file.
                  */
                 int ret = change_in_tz(name);
                 if (ret <= 0) {