Description of problem:
Alexey Dobriyan reported that it is possible to crash a machine by running ftest03 from the LTP test suite (20080630).

The iov_iter_advance() function would look at the iov->iov_len entry even though it might have iterated over the whole array, and iov was pointing past the end.  This would cause DEBUG_PAGEALLOC to trigger a kernel page fault if the allocation was at the end of a page, and the next page was unallocated.

http://lkml.org/lkml/2008/7/30/446