| 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
| ||
|
Date: Wed, 5 Feb 2014 15:00:59 -0500
From: Paul Gortmaker <paul.gortmaker@...driver.com>
To: <stable@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
Avi Kivity <avi@...hat.com>,
Marcelo Tosatti <mtosatti@...hat.com>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [v2.6.34-stable 104/213] mm: mmu_notifier: fix freed page still mapped in secondary MMU
From: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit 3ad3d901bbcfb15a5e4690e55350db0899095a68 upstream.
mmu_notifier_release() is called when the process is exiting. It will
delete all the mmu notifiers. But at this time the page belonging to the
process is still present in page tables and is present on the LRU list, so
this race will happen:
CPU 0 CPU 1
mmu_notifier_release: try_to_unmap:
hlist_del_init_rcu(&mn->hlist);
ptep_clear_flush_notify:
mmu nofifler not found
free page !!!!!!
/*
* At the point, the page has been
* freed, but it is still mapped in
* the secondary MMU.
*/
mn->ops->release(mn, mm);
Then the box is not stable and sometimes we can get this bug:
[ 738.075923] BUG: Bad page state in process migrate-perf pfn:03bec
[ 738.075931] page:ffffea00000efb00 count:0 mapcount:0 mapping: (null) index:0x8076
[ 738.075936] page flags: 0x20000000000014(referenced|dirty)
The same issue is present in mmu_notifier_unregister().
We can call ->release before deleting the notifier to ensure the page has
been unmapped from the secondary MMU before it is freed.
Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc: Avi Kivity <avi@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
mm/mmu_notifier.c | 45 +++++++++++++++++++++++----------------------
1 file changed, 23 insertions(+), 22 deletions(-)
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 438951d366f2..0b54146f986e 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -33,6 +33,24 @@
void __mmu_notifier_release(struct mm_struct *mm)
{
struct mmu_notifier *mn;
+ struct hlist_node *n;
+
+ /*
+ * RCU here will block mmu_notifier_unregister until
+ * ->release returns.
+ */
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist)
+ /*
+ * if ->release runs before mmu_notifier_unregister it
+ * must be handled as it's the only way for the driver
+ * to flush all existing sptes and stop the driver
+ * from establishing any more sptes before all the
+ * pages in the mm are freed.
+ */
+ if (mn->ops->release)
+ mn->ops->release(mn, mm);
+ rcu_read_unlock();
spin_lock(&mm->mmu_notifier_mm->lock);
while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
@@ -46,23 +64,6 @@ void __mmu_notifier_release(struct mm_struct *mm)
* mmu_notifier_unregister to return.
*/
hlist_del_init_rcu(&mn->hlist);
- /*
- * RCU here will block mmu_notifier_unregister until
- * ->release returns.
- */
- rcu_read_lock();
- spin_unlock(&mm->mmu_notifier_mm->lock);
- /*
- * if ->release runs before mmu_notifier_unregister it
- * must be handled as it's the only way for the driver
- * to flush all existing sptes and stop the driver
- * from establishing any more sptes before all the
- * pages in the mm are freed.
- */
- if (mn->ops->release)
- mn->ops->release(mn, mm);
- rcu_read_unlock();
- spin_lock(&mm->mmu_notifier_mm->lock);
}
spin_unlock(&mm->mmu_notifier_mm->lock);
@@ -264,16 +265,13 @@ void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
{
BUG_ON(atomic_read(&mm->mm_count) <= 0);
- spin_lock(&mm->mmu_notifier_mm->lock);
if (!hlist_unhashed(&mn->hlist)) {
- hlist_del_rcu(&mn->hlist);
-
/*
* RCU here will force exit_mmap to wait ->release to finish
* before freeing the pages.
*/
rcu_read_lock();
- spin_unlock(&mm->mmu_notifier_mm->lock);
+
/*
* exit_mmap will block in mmu_notifier_release to
* guarantee ->release is called before freeing the
@@ -282,8 +280,11 @@ void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
if (mn->ops->release)
mn->ops->release(mn, mm);
rcu_read_unlock();
- } else
+
+ spin_lock(&mm->mmu_notifier_mm->lock);
+ hlist_del_rcu(&mn->hlist);
spin_unlock(&mm->mmu_notifier_mm->lock);
+ }
/*
* Wait any running method to finish, of course including
--
1.8.5.2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists