Re:Re: [PATCH] nfsd: fix kernel crash when load nfsd in docker

[Luo Xiaogang]

At 2020-06-24 09:29:01, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
>On Mon, Jun 15, 2020 at 03:12:11PM +0800, Luo Xiaogang wrote:
>> We load nfsd module in the docker container, kernel crash as following.
>> 
>> The 'current->nsproxy->net_ns->gen->ptr[nfsd_net_id]' is overflow in the
>> nfsd_init_net.
>> 
>> We should use the net_ns which is being init in the nfsd_init_net,
>> not the 'current->nsproxy->net_ns'.
>
>Thanks!  Actually, I think my problem was that net init and exit are
>just the wrong place to be doing this--I moved them to nfsd start/stop
>instead.
>
>And then that exposed the fact that I had an inode leak.
>
>Do the following two patches help?

Just test it on Ubuntu 18.04 + Docker 19.03.6, and the docker image is ubuntu:18.04.

Your patchset helps, here is my reported-and-tested-by, Thanks very much.

Reported-and-Tested-by:  Luo Xiaogang <lxgrxd@xxxxxxx>


>--b.
>
>From 16f954bd5c481596a63271a91963bf260e2f3f46 Mon Sep 17 00:00:00 2001
>From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
>Date: Tue, 23 Jun 2020 16:00:33 -0400
>Subject: [PATCH 1/2] nfsd4: fix nfsdfs reference count loop
>
>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.
>
>Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
>---
> 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 bb3d2c32664a..cce2510b2cca 100644
>--- a/fs/nfsd/nfs4state.c
>+++ b/fs/nfsd/nfs4state.c
>@@ -7912,9 +7912,14 @@ 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)
>@@ -7984,6 +7989,7 @@ 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 b68e96681522..cf98a81ca1ea 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 36cdd81b6688..57c832d1b30f 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;
>-- 
>2.26.2
>
>
>From 51de3b460b39e862f7dcfd4d600e8de0afe73e29 Mon Sep 17 00:00:00 2001
>From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
>Date: Tue, 23 Jun 2020 21:01:19 -0400
>Subject: [PATCH 2/2] nfsd: fix nfsdfs inode reference count leak
>
>I don't understand this code well, but  I'm seeing a warning about a
>still-referenced inode on unmount, and every other similar filesystem
>does a dput() here.
>
>Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
>---
> fs/nfsd/nfsctl.c | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
>index cf98a81ca1ea..cd05732f8eaa 100644
>--- a/fs/nfsd/nfsctl.c
>+++ b/fs/nfsd/nfsctl.c
>@@ -1335,6 +1335,7 @@ void nfsd_client_rmdir(struct dentry *dentry)
> 	WARN_ON_ONCE(ret);
> 	fsnotify_rmdir(dir, dentry);
> 	d_delete(dentry);
>+	dput(dentry);
> 	inode_unlock(dir);
> }
> 
>-- 
>2.26.2