Comment 10 for bug 231746

It also does need this patch:

http://www.gossamer-threads.com/lists/linux/kernel/954043#954043
http://kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.26.1

commit a6b79bb88e6682d2739aa5b4db7184038bbb32ce
Author: Linus Torvalds <email address hidden>
Date: Wed Jul 30 22:20:18 2008 +0000

    Fix off-by-one error in iov_iter_advance()

    commit 94ad374a0751f40d25e22e036c37f7263569d24c upstream

    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.

    The quick fix is to just change the order of the tests: check that there
    is any iovec data left before we check the iov entry itself.

    Thanks to Alexey Dobriyan for finding this case, and testing the fix.

    Reported-and-tested-by: Alexey Dobriyan <email address hidden>
    Cc: Nick Piggin <email address hidden>
    Cc: Andrew Morton <email address hidden>
    Signed-off-by: Linus Torvalds <email address hidden>
    Signed-off-by: Greg Kroah-Hartman <email address hidden>