NFS: Ensure we always hold the BKL when dereferencing inode->i_flock

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

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 6e094e95cf0f..0b2a19bfe5a0 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -847,12 +847,19 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
         struct file_lock *fl;
         int status = 0;
 
+        if (inode->i_flock == NULL)
+                return 0;
+
+        /* Guard against delegation returns and new lock/unlock calls */
         down_write(&nfsi->rwsem);
+        /* Protect inode->i_flock using the BKL */
+        lock_kernel();
         for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
                 if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
                         continue;
                 if (nfs_file_open_context(fl->fl_file)->state != state)
                         continue;
+                unlock_kernel();
                 status = ops->recover_lock(state, fl);
                 switch (status) {
                         case 0:
@@ -875,7 +882,9 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
                                 /* kill_proc(fl->fl_pid, SIGLOST, 1); */
                                 status = 0;
                 }
+                lock_kernel();
         }
+        unlock_kernel();
 out:
         up_write(&nfsi->rwsem);
         return status;