On Fri 02-11-18 01:00:07, 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. It is good to mention that interface is root only so the harm due to unbounded allocation request is somehow reduced. I believe we want to use seq_file infrastructure in the long term solution. > Change since v3: > - remove the change in kvmalloc > - keep kmalloc in page_owner.c > > Change since v2: > - improve kvmalloc, allow sub page allocations fallback to > vmalloc when CONFIG_HIGHMEM=y > > Change since v1: > - use kvmalloc() > - clamp buffer size to PAGE_SIZE > > Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx> > Cc: Joe Perches <joe@xxxxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks! > --- > mm/page_owner.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 87bc0dfdb52b..b83f295e4eca 100644 > --- 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; > -- > 2.18.0 > -- Michal Hocko SUSE Labs
