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>
thanks,
greg k-h
