SUNRPC: Fix a potential race in rpc_wake_up_task()

Use RCU to ensure that we can safely call rpc_finish_wakeup after we've
called __rpc_do_wake_up_task. If not, there is a theoretical race, in which
the rpc_task finishes executing, and gets freed first.

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

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index c2e49c397a27..8b58bbf6e39e 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -65,13 +65,19 @@ struct nfs_read_data *nfs_readdata_alloc(size_t len)
         return p;
 }
 
-static void nfs_readdata_free(struct nfs_read_data *p)
+static void nfs_readdata_rcu_free(struct rcu_head *head)
 {
+        struct nfs_read_data *p = container_of(head, struct nfs_read_data, task.u.tk_rcu);
         if (p && (p->pagevec != &p->page_array[0]))
                 kfree(p->pagevec);
         mempool_free(p, nfs_rdata_mempool);
 }
 
+static void nfs_readdata_free(struct nfs_read_data *rdata)
+{
+        call_rcu_bh(&rdata->task.u.tk_rcu, nfs_readdata_rcu_free);
+}
+
 void nfs_readdata_release(void *data)
 {
         nfs_readdata_free(data);