NFS: nfs_igrab_and_active must first reference the superblock

commit 896567ee7f17a8a736cda8a28cc987228410a2ac upstream.

Before referencing the inode, we must ensure that the superblock can be
referenced. Otherwise, we can end up with iput() calling superblock
operations that are no longer valid or accessible.

Fixes: ea7c38fef0b7 ("NFSv4: Ensure we reference the inode for return-on-close in delegreturn")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index f9a4a5524bd580e08213161438bb2ace368dd5db..6f3dc6a5cc7f16eb18e7bb0fbca3934b292eedeb 100644 (file)
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -575,12 +575,14 @@ extern int nfs4_test_session_trunk(struct rpc_clnt *,
 
 static inline struct inode *nfs_igrab_and_active(struct inode *inode)
 {
-       inode = igrab(inode);
-       if (inode != NULL && !nfs_sb_active(inode->i_sb)) {
-               iput(inode);
-               inode = NULL;
+       struct super_block *sb = inode->i_sb;
+
+       if (sb && nfs_sb_active(sb)) {
+               if (igrab(inode))
+                       return inode;
+               nfs_sb_deactive(sb);
        }
-       return inode;
+       return NULL;
 }
 
 static inline void nfs_iput_and_deactive(struct inode *inode)