linux-kernel - [PATCH 5.15 093/171] NFSv4: Handle case where the lookup of a directory fails

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Message-Id: <20220131105233.181528345@linuxfoundation.org>
Date:   Mon, 31 Jan 2022 11:55:58 +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, Lyu Tao <tao.lyu@...l.ch>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>
Subject: [PATCH 5.15 093/171] NFSv4: Handle case where the lookup of a directory fails

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

commit ac795161c93699d600db16c1a8cc23a65a1eceaf upstream.

If the application sets the O_DIRECTORY flag, and tries to open a
regular file, nfs_atomic_open() will punt to doing a regular lookup.
If the server then returns a regular file, we will happily return a
file descriptor with uninitialised open state.

The fix is to return the expected ENOTDIR error in these cases.

Reported-by: Lyu Tao <tao.lyu@...l.ch>
Fixes: 0dd2b474d0b6 ("nfs: implement i_op->atomic_open()")
Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/nfs/dir.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1982,6 +1982,19 @@ out:
 
 no_open:
 	res = nfs_lookup(dir, dentry, lookup_flags);
+	if (!res) {
+		inode = d_inode(dentry);
+		if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
+		    !S_ISDIR(inode->i_mode))
+			res = ERR_PTR(-ENOTDIR);
+	} else if (!IS_ERR(res)) {
+		inode = d_inode(res);
+		if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
+		    !S_ISDIR(inode->i_mode)) {
+			dput(res);
+			res = ERR_PTR(-ENOTDIR);
+		}
+	}
 	if (switched) {
 		d_lookup_done(dentry);
 		if (!res)