Messages in this thread | | | Subject | Re: [PATCH 4.9] mm: page_alloc: validate buddy page before using | From | Xianting Tian <> | Date | Fri, 17 Jun 2022 16:25:35 +0800 |
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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@vger.kernel.org >> Reported-by: zjb194813@alibaba-inc.com >> Reported-by: tianhu.hh@alibaba-inc.com >> Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com> >> --- >> 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@nvidia.com> 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@gandalf.local.home/ Reported-and-tested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Zi Yan <ziy@nvidia.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> > thanks, > > greg k-h
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