On Thu, 2018-11-01 at 14:47 -0700, Andrew Morton wrote: > On Fri, 2 Nov 2018 01:00:07 +0800 <miles.chen@xxxxxxxxxxxx> wrote: > > > From: Miles Chen <miles.chen@xxxxxxxxxxxx> > > > > The page owner read might allocate a large size of memory with > > a large read count. Allocation fails can easily occur when doing > > high order allocations. > > > > Clamp buffer size to PAGE_SIZE to avoid arbitrary size allocation > > and avoid allocation fails due to high order allocation. > > > > ... > > > > --- a/mm/page_owner.c > > +++ b/mm/page_owner.c > > @@ -351,6 +351,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn, > > .skip = 0 > > }; > > > > + count = count > PAGE_SIZE ? PAGE_SIZE : count; > > kbuf = kmalloc(count, GFP_KERNEL); > > if (!kbuf) > > return -ENOMEM; > > A bit tidier: > > --- a/mm/page_owner.c~mm-page_owner-clamp-read-count-to-page_size-fix > +++ a/mm/page_owner.c > @@ -351,7 +351,7 @@ print_page_owner(char __user *buf, size_ > .skip = 0 > }; > > - count = count > PAGE_SIZE ? PAGE_SIZE : count; > + count = min_t(size_t, count, PAGE_SIZE); > kbuf = kmalloc(count, GFP_KERNEL); > if (!kbuf) > return -ENOMEM; A bit tidier still might be if (count > PAGE_SIZE) count = PAGE_SIZE; as that would not always cause a write back to count.
