PROBLEM:        (CLD UVO104419) (Patch ID: OSF375-350251)
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This patch fixes a problem in which the system panics with a kernel memory
fault in k_mem_fault.

This is caused by a user application that calls one of the vectored IO
system calls and passes an invalid kernel address as one of the arguments.
This invalid address is not properly validated by the kernel and therefore
causes the kernel memory fault.

The typical stack traceback is as follows:

 1.) panic(kernel memory fault)
 2.) trap()
 3.) _XentMM()
 4.) k_mem_fault()
 5.) k_map_fault()
 6.) vm_fault()
 7.) trap()
 8.) _XentMM
 9.) bcopy()
 10.) uiomove()
 11.) mmrw()
 12.) mmread()
 13.) spec_read()
 14.) msfsspec_read()
 15.) vn_read()
 16.) rwuio()
 17.) read()   ../src/kernel/bsd/sys_generic.c
 18.) syscall()