Merge branch 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzik/libata-dev
* 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzik/libata-dev:
libata-sff: remove harmful BUG_ON from ata_bmdma_qc_issue
sata_mv: fix broken DSM/TRIM support (v2)
libata: be less of a drama queen on empty data commands
[libata] sata_dwc_460ex: signdness bug
ahci: add HFLAG_YES_FBS and apply it to 88SE9128
libata: remove no longer needed pata_winbond driver
pata_cmd64x: revert commit d62f5576
diff --git a/mm/rmap.c b/mm/rmap.c
index 87b9e8a..f6f0d2d 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -316,7 +316,7 @@
*/
struct anon_vma *page_lock_anon_vma(struct page *page)
{
- struct anon_vma *anon_vma;
+ struct anon_vma *anon_vma, *root_anon_vma;
unsigned long anon_mapping;
rcu_read_lock();
@@ -327,8 +327,21 @@
goto out;
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
- anon_vma_lock(anon_vma);
- return anon_vma;
+ root_anon_vma = ACCESS_ONCE(anon_vma->root);
+ spin_lock(&root_anon_vma->lock);
+
+ /*
+ * If this page is still mapped, then its anon_vma cannot have been
+ * freed. But if it has been unmapped, we have no security against
+ * the anon_vma structure being freed and reused (for another anon_vma:
+ * SLAB_DESTROY_BY_RCU guarantees that - so the spin_lock above cannot
+ * corrupt): with anon_vma_prepare() or anon_vma_fork() redirecting
+ * anon_vma->root before page_unlock_anon_vma() is called to unlock.
+ */
+ if (page_mapped(page))
+ return anon_vma;
+
+ spin_unlock(&root_anon_vma->lock);
out:
rcu_read_unlock();
return NULL;