If find_mergeable_anon_vma() succeeds but another thread installs
->anon_vma before we take ptl, then allocated == NULL but avc should
be freed. Change the code to check avc != NULL to detect this case.
Also, a couple of whitespace changes to make the critical section more
visible.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
mm/rmap.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- 34-rc1/mm/rmap.c~AVP_AVC_LEAK 2010-03-11 13:11:50.000000000 +0100
+++ 34-rc1/mm/rmap.c 2010-04-20 21:05:24.000000000 +0200
@@ -133,8 +133,8 @@ int anon_vma_prepare(struct vm_area_stru
goto out_enomem_free_avc;
allocated = anon_vma;
}
- spin_lock(&anon_vma->lock);
+ spin_lock(&anon_vma->lock);
/* page_table_lock to protect against threads */
spin_lock(&mm->page_table_lock);
if (likely(!vma->anon_vma)) {
@@ -144,14 +144,15 @@ int anon_vma_prepare(struct vm_area_stru
list_add(&avc->same_vma, &vma->anon_vma_chain);
list_add(&avc->same_anon_vma, &anon_vma->head);
allocated = NULL;
+ avc = NULL;
}
spin_unlock(&mm->page_table_lock);
-
spin_unlock(&anon_vma->lock);
- if (unlikely(allocated)) {
+
+ if (unlikely(allocated))
anon_vma_free(allocated);
+ if (unlikely(avc))
anon_vma_chain_free(avc);
- }
}
return 0;
--
