• David S. Miller's avatar
    [IPV4]: Fix byte value boundary check in do_ip_getsockopt(). · 951e07c9
    David S. Miller authored
    This fixes kernel bugzilla 10371.
    
    As reported by M.Piechaczek@osmosys.tv, if we try to grab a
    char sized socket option value, as in:
    
      unsigned char ttl = 255;
      socklen_t     len = sizeof(ttl);
      setsockopt(socket, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, &len);
    
      getsockopt(socket, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, &len);
    
    The ttl returned will be wrong on big-endian, and on both little-
    endian and big-endian the next three bytes in userspace are written
    with garbage.
    
    It's because of this test in do_ip_getsockopt():
    
    	if (len < sizeof(int) && len > 0 && val>=0 && val<255) {
    
    It should allow a 'val' of 255 to pass here, but it doesn't so it
    copies a full 'int' back to userspace.
    
    On little-endian that will write the correct value into the location
    but it spams on the next three bytes in userspace.  On big endian it
    writes the wrong value into the location and spams the next three
    bytes.
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    951e07c9
ip_sockglue.c 26.9 KB