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FAILED: patch "[PATCH] NFS: nfs_delegation_find_inode_server must first reference" failed to apply to 5.4-stable tree

PATCH [email protected] 1 participant 1 message Jan 18, 2021

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The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 113aac6d567bda783af36d08f73bfda47d8e9a40 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <[email protected]>
Date: Sun, 10 Jan 2021 15:46:06 -0500
Subject: [PATCH] NFS: nfs_delegation_find_inode_server must first reference
the superblock

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 Otherwise, we can end up with iput() calling superblock operations that are no longer valid or accessible.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 e39d8a186ed0 ("NFSv4: Fix an Oops during delegation callbacks")
Signed-off-by Trond Myklebust <[email protected]>
fs/nfs/delegation.c +7 -5
index 816e1427f17e..04bf8066980c 100644
@@ -1011,22 +1011,24 @@ nfs_delegation_find_inode_server(struct nfs_server *server,
 				 const struct nfs_fh *fhandle)
 {
 	struct nfs_delegation *delegation;
-	struct inode *freeme, *res = NULL;
+	struct super_block *freeme = NULL;
+	struct inode *res = NULL;
 
 	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
 		spin_lock(&delegation->lock);
 		if (delegation->inode != NULL &&
 		    !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
 		    nfs_compare_fh(fhandle, &NFS_I(delegation->inode)->fh) == 0) {
-			freeme = igrab(delegation->inode);
-			if (freeme && nfs_sb_active(freeme->i_sb))
-				res = freeme;
+			if (nfs_sb_active(server->super)) {
+				freeme = server->super;
+				res = igrab(delegation->inode);
+			}
 			spin_unlock(&delegation->lock);
 			if (res != NULL)
 				return res;
 			if (freeme) {
 				rcu_read_unlock();
-				iput(freeme);
+				nfs_sb_deactive(freeme);
 				rcu_read_lock();
 			}
 			return ERR_PTR(-EAGAIN);