[Devel] [PATCH rh7 v2] binfmt_misc: destroy all nodes on ve stop

[Vladimir Davydov]

Each registered binfmt_misc node pins binfmt_misc mount point, which in
turn pins the owner ve. This means that if we don't clean up binfmt_misc
nodes on ve stop, the mount point as well as the ve struct will leak.

Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
Changes in v2:
 - don't do anything if binfmt_misc was not mounted inside a container
   (i.e. ve->binfmt_misc == NULL)
 - ve_binfmt_fini: s/get_exec_env()/data

 fs/binfmt_misc.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 44871531b810..90c306e84c3f 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -752,16 +752,42 @@ static struct file_system_type bm_fs_type = {
 };
 MODULE_ALIAS_FS("binfmt_misc");
 
+static void ve_binfmt_fini(void *data)
+{
+	struct ve_struct *ve = data;
+	struct binfmt_misc *bm_data = ve->binfmt_misc;
+
+	if (!bm_data)
+		return;
+
+	/*
+	 * XXX: Note we don't take any locks here. This is safe as long as
+	 * nobody uses binfmt_misc outside the owner ve.
+	 */
+	while (!list_empty(&bm_data->entries))
+		kill_node(bm_data, list_first_entry(
+			&bm_data->entries, Node, list));
+}
+
+static struct ve_hook ve_binfmt_hook = {
+	.fini		= ve_binfmt_fini,
+	.priority	= HOOK_PRIO_DEFAULT,
+	.owner		= THIS_MODULE,
+};
+
 static int __init init_misc_binfmt(void)
 {
 	int err = register_filesystem(&bm_fs_type);
-	if (!err)
+	if (!err) {
 		insert_binfmt(&misc_format);
+		ve_hook_register(VE_SS_CHAIN, &ve_binfmt_hook);
+	}
 	return err;
 }
 
 static void __exit exit_misc_binfmt(void)
 {
+	ve_hook_unregister(&ve_binfmt_hook);
 	unregister_binfmt(&misc_format);
 	unregister_filesystem(&bm_fs_type);
 }
-- 
2.1.4