On Fri, Jun 17, 2022 at 04:25:35PM +0800, Xianting Tian wrote:
>
> 在 2022/6/17 下午4:20, Greg KH 写道:
> > On Fri, Jun 17, 2022 at 12:19:28AM +0800, Xianting Tian wrote:
> > > Commit 787af64d05cd ("mm: page_alloc: validate buddy before check its migratetype.")
> > > fixes a bug in 1dd214b8f21c and there is a similar bug in d9dddbf55667 that
> > > can be fixed in a similar way too.
> > >
> > > In addition, for RISC-V arch the first 2MB RAM could be reserved for opensbi,
> > > so it would have pfn_base=512 and mem_map began with 512th PFN when
> > > CONFIG_FLATMEM=y.
> > > But __find_buddy_pfn algorithm thinks the start pfn 0, it could get 0 pfn or
> > > less than the pfn_base value. We need page_is_buddy() to verify the buddy to
> > > prevent accessing an invalid buddy.
> > >
> > > Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Reported-by: zjb194813@xxxxxxxxxxxxxxx
> > > Reported-by: tianhu.hh@xxxxxxxxxxxxxxx
> > > Signed-off-by: Xianting Tian <xianting.tian@xxxxxxxxxxxxxxxxx>
> > > ---
> > > mm/page_alloc.c | 3 +++
> > > 1 file changed, 3 insertions(+)
> > >
> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > index a6e682569e5b..1c423faa4b62 100644
> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -864,6 +864,9 @@ static inline void __free_one_page(struct page *page,
> > > buddy_idx = __find_buddy_index(page_idx, order);
> > > buddy = page + (buddy_idx - page_idx);
> > > +
> > > + if (!page_is_buddy(page, buddy, order))
> > > + goto done_merging;
> > > buddy_mt = get_pageblock_migratetype(buddy);
> > > if (migratetype != buddy_mt
> > > --
> > > 2.17.1
> > >
> > What is the git commit id of this change in Linus's tree?
>
> It is this one,
>
> commit 787af64d05cd528aac9ad16752d11bb1c6061bb9
> Author: Zi Yan <ziy@xxxxxxxxxx>
> Date: Wed Mar 30 15:45:43 2022 -0700
>
> mm: page_alloc: validate buddy before check its migratetype.
>
> Whenever a buddy page is found, page_is_buddy() should be called to
> check its validity. Add the missing check during pageblock merge check.
>
> Fixes: 1dd214b8f21c ("mm: page_alloc: avoid merging non-fallbackable
> pageblocks with others")
> Link:
> https://lore.kernel.org/all/20220330154208.71aca532@xxxxxxxxxxxxxxxxxx/
> Reported-and-tested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>
All now queued up, thanks.
greg k-h
