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[3.13,162/212] mm/memory-failure.c: fix memory leak by race between poison and unpoison

Message ID 1403041506-13646-163-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa June 17, 2014, 9:44 p.m. UTC 
3.13.11.4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

commit 3e030ecc0fc7de10fd0da10c1c19939872a31717 upstream.

When a memory error happens on an in-use page or (free and in-use)
hugepage, the victim page is isolated with its refcount set to one.

When you try to unpoison it later, unpoison_memory() calls put_page()
for it twice in order to bring the page back to free page pool (buddy or
free hugepage list).  However, if another memory error occurs on the
page which we are unpoisoning, memory_failure() returns without
releasing the refcount which was incremented in the same call at first,
which results in memory leak and unconsistent num_poisoned_pages
statistics.  This patch fixes it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 mm/memory-failure.c | 2 ++
 1 file changed, 2 insertions(+)
diff mbox

Patch

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b22effc..3b0855b 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1157,6 +1157,8 @@  int memory_failure(unsigned long pfn, int trapno, int flags)
 	 */
 	if (!PageHWPoison(p)) {
 		printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn);
+		atomic_long_sub(nr_pages, &num_poisoned_pages);
+		put_page(hpage);
 		res = 0;
 		goto out;
 	}