linux-kernel - [PATCH 5.4 55/80] NFS: LOOKUP_DIRECTORY is also ok with symlinks

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Message-Id: <20220221084917.380113774@linuxfoundation.org>
Date:   Mon, 21 Feb 2022 09:49:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Menzel <pmenzel@...gen.mpg.de>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Donald Buczek <buczek@...gen.mpg.de>,
        Anna Schumaker <Anna.Schumaker@...app.com>
Subject: [PATCH 5.4 55/80] NFS: LOOKUP_DIRECTORY is also ok with symlinks

From: Trond Myklebust <trond.myklebust@...merspace.com>

commit e0caaf75d443e02e55e146fd75fe2efc8aed5540 upstream.

Commit ac795161c936 (NFSv4: Handle case where the lookup of a directory
fails) [1], part of Linux since 5.17-rc2, introduced a regression, where
a symbolic link on an NFS mount to a directory on another NFS does not
resolve(?) the first time it is accessed:

Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
Fixes: ac795161c936 ("NFSv4: Handle case where the lookup of a directory fails")
Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Tested-by: Donald Buczek <buczek@...gen.mpg.de>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/nfs/dir.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1641,14 +1641,14 @@ no_open:
 	if (!res) {
 		inode = d_inode(dentry);
 		if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
-		    !S_ISDIR(inode->i_mode))
+		    !(S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)))
 			res = ERR_PTR(-ENOTDIR);
 		else if (inode && S_ISREG(inode->i_mode))
 			res = ERR_PTR(-EOPENSTALE);
 	} else if (!IS_ERR(res)) {
 		inode = d_inode(res);
 		if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
-		    !S_ISDIR(inode->i_mode)) {
+		    !(S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))) {
 			dput(res);
 			res = ERR_PTR(-ENOTDIR);
 		} else if (inode && S_ISREG(inode->i_mode)) {