netfilter: nf_ct_sip: validate Content-Length in TCP SIP messages

[ Upstream commit 274ea0e2a4cdf18110e5931b8ecbfef6353e5293 ]

Verify that the message length of a single SIP message, which is calculated
based on the Content-Length field contained in the SIP message, does not
exceed the packet boundaries.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>