tree dbbecc7be4c616d47586ef0ff6a552c110bcb8d5
parent 619c714c1d6e4dff00ddde582d78492fd95452d6
author David S. Miller <davem@davemloft.net> 1207816176 -0700
committer David S. Miller <davem@davemloft.net> 1207816176 -0700

[IPV4]: Fix byte value boundary check in do_ip_getsockopt().

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: David S. Miller <davem@davemloft.net>