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operations that are no longer valid or accessible.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 8357ff69962f22caae59d1ac357058d89800e963..cc07189a501fab3392d0ae57d0cdd017df0c62f5 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)