This fixes a double-bug in ELF loading, as noticed by Hector Marco-Gisbert. To quote his original email:
The size of the bss section for some interpreters is not correctly calculated resulting in unnecessary calls to vm_brk() with enormous size values. The bug appears when loading some interpreters with a small bss size. Once the last loadable segment has been loaded, the bss section is zeroed up to the page boundary and the elf_bss variable is updated to this new page boundary. Because of this update (alignment), the last_bss could be less than elf_bss and the subtraction "last_bss - elf_bss" value could overflow. ... [e.g.] The size value requested to the vm_brk() call (last_bss - elf_bss) is 0xfffffffffffff938 and internally this size is page aligned in the do_brk() function resulting in a 0 length request. This series takes a slightly different approach to fixing it and updates vm_brk to refuse bad allocation sizes. -Kees
