NFSv4: Fix an oopsable condition in nfs_free_seqid

 Storing a pointer to the struct rpc_task in the nfs_seqid is broken
 since the nfs_seqid may be freed well after the task has been destroyed.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 1 insertions, 9 deletions

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 8a3788199052..45bff1d1a513 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -112,7 +112,6 @@ struct nfs_seqid_counter {
 struct nfs_seqid {
         struct list_head list;
         struct nfs_seqid_counter *sequence;
-        struct rpc_task *task;
 };
 
 static inline void nfs_confirm_seqid(struct nfs_seqid_counter *seqid, int status)
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 23834c8fb740..da0861db57fb 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -676,7 +676,6 @@ struct nfs_seqid *nfs_alloc_seqid(struct nfs_seqid_counter *counter)
         new = kmalloc(sizeof(*new), GFP_KERNEL);
         if (new != NULL) {
                 new->sequence = counter;
-                new->task = NULL;
                 spin_lock(&sequence->lock);
                 list_add_tail(&new->list, &sequence->list);
                 spin_unlock(&sequence->lock);
@@ -687,15 +686,10 @@ struct nfs_seqid *nfs_alloc_seqid(struct nfs_seqid_counter *counter)
 void nfs_free_seqid(struct nfs_seqid *seqid)
 {
         struct rpc_sequence *sequence = seqid->sequence->sequence;
-        struct rpc_task *next = NULL;
 
         spin_lock(&sequence->lock);
         list_del(&seqid->list);
-        if (!list_empty(&sequence->list)) {
-                next = list_entry(sequence->list.next, struct nfs_seqid, list)->task;
-                if (next)
-                        rpc_wake_up_task(next);
-        }
+        rpc_wake_up(&sequence->wait);
         spin_unlock(&sequence->lock);
         kfree(seqid);
 }
@@ -754,7 +748,6 @@ int nfs_wait_on_sequence(struct nfs_seqid *seqid, struct rpc_task *task)
 
         spin_lock(&sequence->lock);
         if (sequence->list.next != &seqid->list) {
-                seqid->task = task;
                 rpc_sleep_on(&sequence->wait, task, NULL, NULL);
                 status = -EAGAIN;
         }