nfsd: don't return an unhashed lock stateid after taking mutex

BugLink: http://bugs.launchpad.net/bugs/1615620
commit dd257933fa4b9fea66a1195f8a15111029810abc upstream.

nfsd4_lock will take the st_mutex before working with the stateid it
gets, but between the time when we drop the cl_lock and take the mutex,
the stateid could become unhashed (a'la FREE_STATEID). If that happens
the lock stateid returned to the client will be forgotten.

Fix this by first moving the st_mutex acquisition into
lookup_or_create_lock_state. Then, have it check to see if the lock
stateid is still hashed after taking the mutex. If it's not, then put
the stateid and try the find/create again.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Tested-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 38e353dfba4b7e1df266d20edc0eb8c85a42aaa6..f7ea624780a7cdc18d725e171dd3a1b47b371129 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5502,7 +5502,7 @@ static __be32
 lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
                            struct nfs4_ol_stateid *ost,
                            struct nfsd4_lock *lock,
-                           struct nfs4_ol_stateid **lst, bool *new)
+                           struct nfs4_ol_stateid **plst, bool *new)
 {
        __be32 status;
        struct nfs4_file *fi = ost->st_stid.sc_file;
@@ -5510,7 +5510,9 @@ lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
        struct nfs4_client *cl = oo->oo_owner.so_client;
        struct inode *inode = d_inode(cstate->current_fh.fh_dentry);
        struct nfs4_lockowner *lo;
+       struct nfs4_ol_stateid *lst;
        unsigned int strhashval;
+       bool hashed;
 
        lo = find_lockowner_str(cl, &lock->lk_new_owner);
        if (!lo) {
@@ -5526,12 +5528,27 @@ lookup_or_create_lock_state(struct nfsd4_compound_state *cstate,
                        goto out;
        }
 
-       *lst = find_or_create_lock_stateid(lo, fi, inode, ost, new);
-       if (*lst == NULL) {
+retry:
+       lst = find_or_create_lock_stateid(lo, fi, inode, ost, new);
+       if (lst == NULL) {
                status = nfserr_jukebox;
                goto out;
        }
+
+       mutex_lock(&lst->st_mutex);
+
+       /* See if it's still hashed to avoid race with FREE_STATEID */
+       spin_lock(&cl->cl_lock);
+       hashed = !list_empty(&lst->st_perfile);
+       spin_unlock(&cl->cl_lock);
+
+       if (!hashed) {
+               mutex_unlock(&lst->st_mutex);
+               nfs4_put_stid(&lst->st_stid);
+               goto retry;
+       }
        status = nfs_ok;
+       *plst = lst;
 out:
        nfs4_put_stateowner(&lo->lo_owner);
        return status;
@@ -5598,8 +5615,6 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
                        goto out;
                status = lookup_or_create_lock_state(cstate, open_stp, lock,
                                                        &lock_stp, &new);
-               if (status == nfs_ok)
-                       mutex_lock(&lock_stp->st_mutex);
        } else {
                status = nfs4_preprocess_seqid_op(cstate,
                                       lock->lk_old_lock_seqid,