mempolicy: fix refcount leak in mpol_set_shared_policy()

When shared_policy_replace() fails to allocate new->policy is not freed
correctly by mpol_set_shared_policy().  The problem is that shared
mempolicy code directly call kmem_cache_free() in multiple places where
it is easy to make a mistake.

This patch creates an sp_free wrapper function and uses it. The bug was
introduced pre-git age (IOW, before 2.6.12-rc2).

[mgorman@suse.de: Editted changelog]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Christoph Lameter <cl@linux.com>
Cc: Josh Boyer <jwboyer@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 6 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index b2f12ecc1b34..1763418f1ada 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2157,12 +2157,17 @@ mpol_shared_policy_lookup(struct shared_policy *sp, unsigned long idx)
         return pol;
 }
 
+static void sp_free(struct sp_node *n)
+{
+        mpol_put(n->policy);
+        kmem_cache_free(sn_cache, n);
+}
+
 static void sp_delete(struct shared_policy *sp, struct sp_node *n)
 {
         pr_debug("deleting %lx-l%lx\n", n->start, n->end);
         rb_erase(&n->nd, &sp->root);
-        mpol_put(n->policy);
-        kmem_cache_free(sn_cache, n);
+        sp_free(n);
 }
 
 static struct sp_node *sp_alloc(unsigned long start, unsigned long end,
@@ -2301,7 +2306,7 @@ int mpol_set_shared_policy(struct shared_policy *info,
         }
         err = shared_policy_replace(info, vma->vm_pgoff, vma->vm_pgoff+sz, new);
         if (err && new)
-                kmem_cache_free(sn_cache, new);
+                sp_free(new);
         return err;
 }
 
@@ -2318,9 +2323,7 @@ void mpol_free_shared_policy(struct shared_policy *p)
         while (next) {
                 n = rb_entry(next, struct sp_node, nd);
                 next = rb_next(&n->nd);
-                rb_erase(&n->nd, &p->root);
-                mpol_put(n->policy);
-                kmem_cache_free(sn_cache, n);
+                sp_delete(p, n);
         }
         mutex_unlock(&p->mutex);
 }