linux-kernel - [PATCH 5.4] mm: page_alloc: validate buddy page before using

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220616161746.3565225-4-xianting.tian@linux.alibaba.com>
Date:   Fri, 17 Jun 2022 00:17:43 +0800
From:   Xianting Tian <xianting.tian@...ux.alibaba.com>
To:     akpm@...ux-foundation.org, ziy@...dia.com,
        gregkh@...uxfoundation.org, stable@...r.kernel.org,
        guoren@...nel.org
Cc:     huanyi.xj@...baba-inc.com, guohanjun@...wei.com,
        zjb194813@...baba-inc.com, tianhu.hh@...baba-inc.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Xianting Tian <xianting.tian@...ux.alibaba.com>
Subject: [PATCH 5.4] mm: page_alloc: validate buddy page before using

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@...r.kernel.org
Reported-by: zjb194813@...baba-inc.com
Reported-by: tianhu.hh@...baba-inc.com
Signed-off-by: Xianting Tian <xianting.tian@...ux.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 f08ce248af2a..8f56e6a193cc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -959,6 +959,9 @@ 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))
+				goto done_merging;
 			buddy_mt = get_pageblock_migratetype(buddy);
 
 			if (migratetype != buddy_mt
-- 
2.17.1