From be46326d9c6556a79e33e87be67410da8e5e3598 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Wed, 29 Sep 2021 08:12:53 -0400
Subject: [PATCH] NFS: Fix dentry verifier races
Git-commit: cec08f452a687fce9dfdf47946d00a1d12a8bec5
Patch-mainline: v5.16-rc1
References: stable-5.14.19

[ Upstream commit cec08f452a687fce9dfdf47946d00a1d12a8bec5 ]

If the directory changed while we were revalidating the dentry, then
don't update the dentry verifier. There is no value in setting the
verifier to an older value, and we could end up overwriting a more up to
date verifier from a parallel revalidation.

Fixes: efeda80da38d ("NFSv4: Fix revalidation of dentries with delegations")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Tested-by: Benjamin Coddington <bcodding@redhat.com>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 fs/nfs/dir.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 085b8ecdc17d..5b68c44848ca 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1269,13 +1269,12 @@ static bool nfs_verifier_is_delegated(struct dentry *dentry)
 static void nfs_set_verifier_locked(struct dentry *dentry, unsigned long verf)
 {
 	struct inode *inode = d_inode(dentry);
+	struct inode *dir = d_inode(dentry->d_parent);
 
-	if (!nfs_verifier_is_delegated(dentry) &&
-	    !nfs_verify_change_attribute(d_inode(dentry->d_parent), verf))
-		goto out;
+	if (!nfs_verify_change_attribute(dir, verf))
+		return;
 	if (inode && NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
 		nfs_set_verifier_delegated(&verf);
-out:
 	dentry->d_time = verf;
 }
 
-- 
2.26.2