From: Guo Ren <guoren@kernel.org>
To: Xianting Tian <xianting.tian@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
ziy@nvidia.com, Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
stable@vger.kernel.org, huanyi.xj@alibaba-inc.com,
zjb194813@alibaba-inc.com, tianhu.hh@alibaba-inc.com
Subject: Re: [RESEND PATCH] mm: page_alloc: validate buddy before check the migratetype
Date: Tue, 14 Jun 2022 00:08:50 +0800 [thread overview]
Message-ID: <CAJF2gTQJZFfpSOx0yo3zJfECwpZR=79F5uLKVV_qqopS+F2PYA@mail.gmail.com> (raw)
In-Reply-To: <20220613131046.3009889-1-xianting.tian@linux.alibaba.com>
On Mon, Jun 13, 2022 at 9:11 PM Xianting Tian
<xianting.tian@linux.alibaba.com> wrote:
>
> Commit 787af64d05cd ("mm: page_alloc: validate buddy before check its migratetype.")
> added buddy check code. But unfortunately, this fix isn't backported to
> linux-5.17.y and the former stable branches. The reason is it added wrong
> fixes message:
> Fixes: 1dd214b8f21c ("mm: page_alloc: avoid merging non-fallbackable
> pageblocks with others")
> Actually, this issue is involved by commit:
> commit d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
>
> For RISC-V arch, the first 2M is reserved for sbi, so the start PFN is 512,
> but it got buddy PFN 0 for PFN 0x2000:
> 0 = 0x2000 ^ (1 << 12)
How did we get 0? (Try it in gdb)
(gdb) p /x (0x2000 ^ (1<<12))
$3 = 0x3000
I think it got buddy PFN 0 for PFN 0x1000, right?
(gdb) p /x (0x1000 ^ (1<<12))
$4 = 0x0
> With the illegal buddy PFN 0, it got an illegal buddy page, which caused
> crash in __get_pfnblock_flags_mask().
>
> With the patch, it can avoid the calling of get_pageblock_migratetype() if
> it isn't buddy page.
>
> 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 b1caa1c6c887..5b423caa68fd 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1129,6 +1129,9 @@ static inline void __free_one_page(struct page *page,
>
> buddy_pfn = __find_buddy_pfn(pfn, order);
> buddy = page + (buddy_pfn - pfn);
> +
> + if (!page_is_buddy(page, buddy, order))
Right, we need to check the buddy_pfn valid, because some SoCs would
start dram address with an offset that has an order smaller than
MAX_ORDER.
> + goto done_merging;
> buddy_mt = get_pageblock_migratetype(buddy);
>
> if (migratetype != buddy_mt
> --
> 2.17.1
>
Fixup the comment and
Reviewed-by: Guo Ren <guoren@kernel.org>
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
next prev parent reply other threads:[~2022-06-13 18:59 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-13 13:10 [RESEND PATCH] mm: page_alloc: validate buddy before check the migratetype Xianting Tian
2022-06-13 15:22 ` Zi Yan
2022-06-13 16:32 ` Guo Ren
2022-06-13 19:49 ` Zi Yan
2022-06-13 23:47 ` Guo Ren
2022-06-14 0:14 ` Zi Yan
2022-06-14 1:19 ` Guo Ren
2022-06-14 3:26 ` Xianting Tian
2022-06-15 6:47 ` Xianting Tian
2022-06-15 13:55 ` Zi Yan
2022-06-15 16:15 ` Xianting Tian
2022-06-16 1:51 ` Xianting Tian
2022-06-16 14:01 ` Zi Yan
2022-06-16 15:04 ` David Hildenbrand
2022-06-16 15:16 ` Xianting Tian
2022-06-17 3:17 ` Guo Ren
2022-06-13 16:08 ` Guo Ren [this message]
2022-06-14 1:26 ` Xianting Tian
2022-06-14 2:04 ` Xianting Tian
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAJF2gTQJZFfpSOx0yo3zJfECwpZR=79F5uLKVV_qqopS+F2PYA@mail.gmail.com' \
--to=guoren@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=huanyi.xj@alibaba-inc.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=stable@vger.kernel.org \
--cc=tianhu.hh@alibaba-inc.com \
--cc=vbabka@suse.cz \
--cc=xianting.tian@linux.alibaba.com \
--cc=ziy@nvidia.com \
--cc=zjb194813@alibaba-inc.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).