From 212bf41d88c06afc23e03f9b274eebf1e8dba197 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 12:53:38 +0300 Subject: fs, nfs: convert nfs_client.cl_count from atomic_t to refcount_t atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable nfs_client.cl_count is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: Anna Schumaker --- fs/nfs/client.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'fs/nfs/client.c') diff --git a/fs/nfs/client.c b/fs/nfs/client.c index 22880ef6d8dd..0ac2fb1c6b63 100644 --- a/fs/nfs/client.c +++ b/fs/nfs/client.c @@ -163,7 +163,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init) clp->rpc_ops = clp->cl_nfs_mod->rpc_ops; - atomic_set(&clp->cl_count, 1); + refcount_set(&clp->cl_count, 1); clp->cl_cons_state = NFS_CS_INITING; memcpy(&clp->cl_addr, cl_init->addr, cl_init->addrlen); @@ -269,7 +269,7 @@ void nfs_put_client(struct nfs_client *clp) nn = net_generic(clp->cl_net, nfs_net_id); - if (atomic_dec_and_lock(&clp->cl_count, &nn->nfs_client_lock)) { + if (refcount_dec_and_lock(&clp->cl_count, &nn->nfs_client_lock)) { list_del(&clp->cl_share_link); nfs_cb_idr_remove_locked(clp); spin_unlock(&nn->nfs_client_lock); @@ -314,7 +314,7 @@ static struct nfs_client *nfs_match_client(const struct nfs_client_initdata *dat sap)) continue; - atomic_inc(&clp->cl_count); + refcount_inc(&clp->cl_count); return clp; } return NULL; @@ -1006,7 +1006,7 @@ struct nfs_server *nfs_clone_server(struct nfs_server *source, /* Copy data from the source */ server->nfs_client = source->nfs_client; server->destroy = source->destroy; - atomic_inc(&server->nfs_client->cl_count); + refcount_inc(&server->nfs_client->cl_count); nfs_server_copy_userdata(server, source); server->fsid = fattr->fsid; @@ -1166,7 +1166,7 @@ static int nfs_server_list_show(struct seq_file *m, void *v) clp->rpc_ops->version, rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_ADDR), rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_PORT), - atomic_read(&clp->cl_count), + refcount_read(&clp->cl_count), clp->cl_hostname); rcu_read_unlock(); -- cgit v1.2.2