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  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]
Date:	Fri, 23 Aug 2013 18:30:37 +0800
From:	Wanpeng Li <>
To:	Andrew Morton <>
Cc:	Andi Kleen <>,
	Fengguang Wu <>,
	Naoya Horiguchi <>,
	Tony Luck <>,,,,
	Wanpeng Li <>
Subject: [PATCH v2 3/7] mm/hwpoison: fix race against poison thp

v1 -> v2:
	* unpoison thp fail  

There is a race between hwpoison page and unpoison page, memory_failure
set the page hwpoison and increase num_poisoned_pages without hold page
lock, and one page count will be accounted against thp for num_poisoned_pages.
However, unpoison can occur before memory_failure hold page lock and
split transparent hugepage, unpoison will decrease num_poisoned_pages
by 1 << compound_order since memory_failure has not yet split transparent
hugepage with page lock held. That means we account one page for hwpoison
and 1 << compound_order for unpoison. This patch fix it by inserting a 
PageTransHuge check before doing TestClearPageHWPoison, unpoison failed 
without clearing PageHWPoison and decreasing num_poisoned_pages.

            A                                                 	B
        if (PageHuge(p))
            nr_pages = 1 << compound_order(hpage);
            nr_pages = 1;
        atomic_long_add(nr_pages, &num_poisoned_pages);
	                                                        nr_pages = 1<< compound_trans_order(page);
                                                            atomic_long_sub(nr_pages, &num_poisoned_pages);
        lock page
        if (!PageHWPoison(p))
        	unlock page and return
        if (PageTransHuge(hpage))

Suggested-by: Naoya Horiguchi <>
Signed-off-by: Wanpeng Li <>
 mm/memory-failure.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5a4f4d6..a6c4752 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1339,6 +1339,16 @@ int unpoison_memory(unsigned long pfn)
 		return 0;
+	/*
+	 * unpoison_memory() can encounter thp only when the thp is being
+	 * worked by memory_failure() and the page lock is not held yet.
+	 * In such case, we yield to memory_failure() and make unpoison fail.
+	 */
+	if (PageTransHuge(page)) {
+		pr_info("MCE: Memory failure is now running on %#lx\n", pfn);
+			return 0;
+	}
 	nr_pages = 1 << compound_order(page);
 	if (!get_page_unless_zero(page)) {

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists