I think both patches are fine, just a question.
On 07/08, Kees Cook wrote:
>
> -static int do_brk(unsigned long addr, unsigned long len)
> +static int do_brk(unsigned long addr, unsigned long request)
> {
> struct mm_struct *mm = current->mm;
> struct vm_area_struct *vma, *prev;
> - unsigned long flags;
> + unsigned long flags, len;
> struct rb_node **rb_link, *rb_parent;
> pgoff_t pgoff = addr >> PAGE_SHIFT;
> int error;
>
> - len = PAGE_ALIGN(len);
> + len = PAGE_ALIGN(request);
> + if (len < request)
> + return -ENOMEM;
So iiuc "len < request" is only possible if len == 0, right?
> if (!len)
> return 0;
and thus this patch fixes the error code returned by do_brk() in case
of overflow, now it returns -ENOMEM rather than zero. Perhaps
if (!len)
return 0;
len = PAGE_ALIGN(len);
if (!len)
return -ENOMEM;
would be more clear but this is subjective.
I am wondering if we should shift this overflow check to the caller(s).
Say, sys_brk() does find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE)
before do_brk(), and in case of overflow find_vma_intersection() can
wrongly return NULL.
Then do_brk() will be called with len = -oldbrk, this can overflow or
not but in any case this doesn't look right too.
Or I am totally confused?
Oleg.
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