The patch below does not apply to the 5.5-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 75da98586af75eb80664714a67a9895bf0a5517e Mon Sep 17 00:00:00 2001
From: Trond Myklebust trond.myklebust@hammerspace.com Date: Thu, 2 Apr 2020 10:34:36 -0400 Subject: [PATCH] NFS: finish_automount() requires us to hold 2 refs to the mount record
We must not return from nfs_d_automount() without holding 2 references to the mount record. Doing so, will trigger the BUG() in finish_automount(). Also ensure that we don't try to reschedule the automount timer with a negative or zero timeout value.
Fixes: 22a1ae9a93fb ("NFS: If nfs_mountpoint_expiry_timeout < 0, do not expire submounts") Cc: stable@vger.kernel.org # v5.5+ Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c index da67820462f2..fe19ae280262 100644 --- a/fs/nfs/namespace.c +++ b/fs/nfs/namespace.c @@ -145,6 +145,7 @@ struct vfsmount *nfs_d_automount(struct path *path) struct vfsmount *mnt = ERR_PTR(-ENOMEM); struct nfs_server *server = NFS_SERVER(d_inode(path->dentry)); struct nfs_client *client = server->nfs_client; + int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout); int ret;
if (IS_ROOT(path->dentry)) @@ -190,12 +191,12 @@ struct vfsmount *nfs_d_automount(struct path *path) if (IS_ERR(mnt)) goto out_fc;
- if (nfs_mountpoint_expiry_timeout < 0) + mntget(mnt); /* prevent immediate expiration */ + if (timeout <= 0) goto out_fc;
- mntget(mnt); /* prevent immediate expiration */ mnt_set_expiry(mnt, &nfs_automount_list); - schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); + schedule_delayed_work(&nfs_automount_task, timeout);
out_fc: put_fs_context(fc); @@ -233,10 +234,11 @@ const struct inode_operations nfs_referral_inode_operations = { static void nfs_expire_automounts(struct work_struct *work) { struct list_head *list = &nfs_automount_list; + int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
mark_mounts_for_expiry(list); - if (!list_empty(list)) - schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); + if (!list_empty(list) && timeout > 0) + schedule_delayed_work(&nfs_automount_task, timeout); }
void nfs_release_automount_timer(void)