From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Fri, 28 Sep 2012 00:19:11 +0000 (+1000)
Subject: mempolicy: fix refcount leak in mpol_set_shared_policy()
X-Git-Tag: next-20120928~1^2~345
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a071d27d9463c6037c2628c4dad6d82679906b4d;p=karo-tx-linux.git

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>
---

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index a0eec0e65dbf..a31d6b519f6f 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2250,12 +2250,17 @@ out:
 	return ret;
 }
 
+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,
@@ -2394,7 +2399,7 @@ 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;
 }
 
@@ -2411,9 +2416,7 @@ 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);
 }