[PATCH 4/6] mempolicy: fix refcount leak in mpol_set_shared_policy()

kosaki.motohiro
2012-06-11T09:18:37Z

From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

When shared_policy_replace() failure, new->policy is not freed correctly.
The real problem is, shared mempolicy codes directly call kmem_cache_free()
in multiple place.

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

Cc: Dave Jones <davej@redhat.com>,
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>,
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
mm/mempolicy.c | 15 +++++++++------
1 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d97d2db..7fb7d51 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2150,12 +2150,17 @@ 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 void sp_node_init(struct sp_node *node, unsigned long start,
@@ -2320,7 +2325,7 @@ 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;
}

@@ -2337,9 +2342,7 @@ 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);
}
spin_unlock(&p->lock);
}
--
1.7.1