net: validate variable length ll headers
[ Upstream commit 2793a23a ] Netdevice parameter hard_header_len is variously interpreted both as an upper and lower bound on link layer header length. The field is used as upper bound when reserving room at allocation, as lower bound when validating user input in PF_PACKET. Clarify the definition to be maximum header length. For validation of untrusted headers, add an optional validate member to header_ops. Allow bypassing of validation by passing CAP_SYS_RAWIO, for instance for deliberate testing of corrupt input. In this case, pad trailing bytes, as some device drivers expect completely initialized headers. See also http://comments.gmane.org/gmane.linux.network/401064Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Kamal Mostafa <kamal@canonical.com>
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