[PATCH 4.9 11/24] NFS prevent double free in async nfs4_exchange_id

Greg Kroah-Hartman
2017-03-24T18:23:35Z

From: Olga Kornievskaia <kolga@netapp.com>

commit 63513232f8cd219dcaa5eafae028740ed3067d83 upstream.

Since rpc_task is async, the release function should be called which
will free the impl_id, scope, and owner.

Trond pointed at 2 more problems:
-- use of client pointer after free in the nfs4_exchangeid_release() function
-- cl_count mismatch if rpc_run_task() isn't run

Fixes: 8d89bd70bc9 ("NFS setup async exchange_id")
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/nfs4proc.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7426,11 +7426,11 @@ static void nfs4_exchange_id_release(voi
struct nfs41_exchange_id_data *cdata =
(struct nfs41_exchange_id_data *)data;

- nfs_put_client(cdata->args.client);
if (cdata->xprt) {
xprt_put(cdata->xprt);
rpc_clnt_xprt_switch_put(cdata->args.client->cl_rpcclient);
}
+ nfs_put_client(cdata->args.client);
kfree(cdata->res.impl_id);
kfree(cdata->res.server_scope);
kfree(cdata->res.server_owner);
@@ -7537,10 +7537,8 @@ static int _nfs4_proc_exchange_id(struct
task_setup_data.callback_data = calldata;

task = rpc_run_task(&task_setup_data);
- if (IS_ERR(task)) {
- status = PTR_ERR(task);
- goto out_impl_id;
- }
+ if (IS_ERR(task))
+ return PTR_ERR(task);

if (!xprt) {
status = rpc_wait_for_completion_task(task);
@@ -7568,6 +7566,7 @@ out_server_owner:
kfree(calldata->res.server_owner);
out_calldata:
kfree(calldata);
+ nfs_put_client(clp);
goto out;
}