binfmt_elf: use vmalloc() for allocation of vma_filesz

binfmt_elf: use vmalloc() for allocation of vma_filesz

We have observed page allocations failures of order 4 during core dump
while trying to allocate vma_filesz.  This results in a useless core
file of size 0.  To improve reliability use vmalloc().

Note that the vmalloc() allocation is bounded by sysctl_max_map_count,
which is 65,530 by default.  So with a 4k page size, and 8 bytes per
seg, this is a max of 128 pages or an order 7 allocation.  Other parts
of the core dump path, such as fill_files_note() are already using
vmalloc() for presumably similar reasons.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jason Baron <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>