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NFS: finish_automount() requires us to hold 2 refs to the mount record

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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: 22a1ae9a93 ("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>
This commit is contained in:
Trond Myklebust 2020-04-02 10:34:36 -04:00
parent 529af90576
commit 75da98586a
1 changed files with 7 additions and 5 deletions
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12
fs/nfs/namespace.c
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@ -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)