[CVE-2011-1748] can: add missing socket check in can/raw release

[Andy Whitcroft]

CVE-2011-1748
	The raw_release function in net/can/raw.c in the Linux kernel
	before 2.6.39-rc6 does not properly validate a socket data
	structure, which allows local users to cause a denial of service
	(NULL pointer dereference) or possibly have unspecified other
	impact via a crafted release operation.

The fix for this issue is already applied to Oneiric, Natty, and Lucid
arriving via mainline/stable updates.  Neither of Hardy or Dapper
contain the affected protocol.  Following this email is a patch for
Maverick cherry-picked from mainline.

Proposing for Maverick.

-apw