From: Qian Cai <cai@lca.pw>
To: akpm@linux-foundation.org
Cc: glider@google.com, keescook@chromium.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH -next v2] mm/page_alloc: fix a false memory corruption
Date: Thu, 20 Jun 2019 16:46:06 -0400 [thread overview]
Message-ID: <1561063566-16335-1-git-send-email-cai@lca.pw> (raw)
The linux-next commit "mm: security: introduce init_on_alloc=1 and
init_on_free=1 boot options" [1] introduced a false positive when
init_on_free=1 and page_poison=on, due to the page_poison expects the
pattern 0xaa when allocating pages which were overwritten by
init_on_free=1 with 0.
Fix it by switching the order between kernel_init_free_pages() and
kernel_poison_pages() in free_pages_prepare().
[1] https://patchwork.kernel.org/patch/10999465/
Signed-off-by: Qian Cai <cai@lca.pw>
---
v2: After further debugging, the issue after switching order is likely a
separate issue as clear_page() should not cause issues with future
accesses.
mm/page_alloc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 54dacf35d200..32bbd30c5f85 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1172,9 +1172,10 @@ static __always_inline bool free_pages_prepare(struct page *page,
PAGE_SIZE << order);
}
arch_free_page(page, order);
- kernel_poison_pages(page, 1 << order, 0);
if (want_init_on_free())
kernel_init_free_pages(page, 1 << order);
+
+ kernel_poison_pages(page, 1 << order, 0);
if (debug_pagealloc_enabled())
kernel_map_pages(page, 1 << order, 0);
--
1.8.3.1
next reply other threads:[~2019-06-20 20:46 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-20 20:46 Qian Cai [this message]
2019-06-21 1:01 ` [PATCH -next v2] mm/page_alloc: fix a false memory corruption Kees Cook
2019-06-21 10:39 ` Alexander Potapenko
2019-06-21 12:26 ` Qian Cai
2019-06-21 14:37 ` Alexander Potapenko
2019-06-21 14:56 ` Qian Cai
2019-06-21 15:26 ` Alexander Potapenko
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