[PATCH 5.7 072/112] nfsd4: fix nfsdfs reference count loop

Greg Kroah-Hartman
2020-07-07T15:25:22Z

From: J. Bruce Fields <bfields@redhat.com>

[ Upstream commit 681370f4b00af0fcc65bbfb9f82de526ab7ceb0a ]

We don't drop the reference on the nfsdfs filesystem with
mntput(nn->nfsd_mnt) until nfsd_exit_net(), but that won't be called
until the nfsd module's unloaded, and we can't unload the module as long
as there's a reference on nfsdfs. So this prevents module unloading.

Fixes: 2c830dd7209b ("nfsd: persist nfsd filesystem across mounts")
Reported-and-Tested-by: Luo Xiaogang <lxgrxd@163.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfsd/nfs4state.c | 8 +++++++-
fs/nfsd/nfsctl.c | 22 ++++++++++++----------
fs/nfsd/nfsd.h | 3 +++
3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index f71e5590967bb..95e459a1dd7dc 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -7873,9 +7873,14 @@ nfs4_state_start_net(struct net *net)
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
int ret;

- ret = nfs4_state_create_net(net);
+ ret = get_nfsdfs(net);
if (ret)
return ret;
+ ret = nfs4_state_create_net(net);
+ if (ret) {
+ mntput(nn->nfsd_mnt);
+ return ret;
+ }
locks_start_grace(net, &nn->nfsd4_manager);
nfsd4_client_tracking_init(net);
if (nn->track_reclaim_completes && nn->reclaim_str_hashtbl_size == 0)
@@ -7944,6 +7949,7 @@ nfs4_state_shutdown_net(struct net *net)

nfsd4_client_tracking_exit(net);
nfs4_state_destroy_net(net);
+ mntput(nn->nfsd_mnt);
}

void
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 71687d99b0901..9b22d857549c3 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1424,6 +1424,18 @@ static struct file_system_type nfsd_fs_type = {
};
MODULE_ALIAS_FS("nfsd");

+int get_nfsdfs(struct net *net)
+{
+ struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct vfsmount *mnt;
+
+ mnt = vfs_kern_mount(&nfsd_fs_type, SB_KERNMOUNT, "nfsd", NULL);
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+ nn->nfsd_mnt = mnt;
+ return 0;
+}
+
#ifdef CONFIG_PROC_FS
static int create_proc_exports_entry(void)
{
@@ -1451,7 +1463,6 @@ unsigned int nfsd_net_id;
static __net_init int nfsd_init_net(struct net *net)
{
int retval;
- struct vfsmount *mnt;
struct nfsd_net *nn = net_generic(net, nfsd_net_id);

retval = nfsd_export_init(net);
@@ -1478,16 +1489,8 @@ static __net_init int nfsd_init_net(struct net *net)
init_waitqueue_head(&nn->ntf_wq);
seqlock_init(&nn->boot_lock);

- mnt = vfs_kern_mount(&nfsd_fs_type, SB_KERNMOUNT, "nfsd", NULL);
- if (IS_ERR(mnt)) {
- retval = PTR_ERR(mnt);
- goto out_mount_err;
- }
- nn->nfsd_mnt = mnt;
return 0;

-out_mount_err:
- nfsd_reply_cache_shutdown(nn);
out_drc_error:
nfsd_idmap_shutdown(net);
out_idmap_error:
@@ -1500,7 +1503,6 @@ static __net_exit void nfsd_exit_net(struct net *net)
{
struct nfsd_net *nn = net_generic(net, nfsd_net_id);

- mntput(nn->nfsd_mnt);
nfsd_reply_cache_shutdown(nn);
nfsd_idmap_shutdown(net);
nfsd_export_shutdown(net);
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index 36cdd81b6688a..57c832d1b30fd 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -90,6 +90,8 @@ void nfsd_destroy(struct net *net);

bool i_am_nfsd(void);

+int get_nfsdfs(struct net *);
+
struct nfsdfs_client {
struct kref cl_ref;
void (*cl_release)(struct kref *kref);
@@ -100,6 +102,7 @@ struct dentry *nfsd_client_mkdir(struct nfsd_net *nn,
struct nfsdfs_client *ncl, u32 id, const struct tree_descr *);
void nfsd_client_rmdir(struct dentry *dentry);

+
#if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL)
#ifdef CONFIG_NFSD_V2_ACL
extern const struct svc_version nfsd_acl_version2;
--
2.25.1