linux-kernel - [PATCH v2 8/9] fs/fuse: properly handle idmapped ->rename op

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Message-Id: <20240814114034.113953-9-aleksandr.mikhalitsyn@canonical.com>
Date: Wed, 14 Aug 2024 13:40:33 +0200
From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
To: mszeredi@...hat.com
Cc: brauner@...nel.org,
	stgraber@...raber.org,
	linux-fsdevel@...r.kernel.org,
	Seth Forshee <sforshee@...nel.org>,
	Miklos Szeredi <miklos@...redi.hu>,
	Amir Goldstein <amir73il@...il.com>,
	Bernd Schubert <bschubert@....com>,
	Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 8/9] fs/fuse: properly handle idmapped ->rename op

Support of RENAME_WHITEOUT with idmapped mounts requires
an API extension for FUSE_RENAME2.

Let's just forbid this combination for now. It's not
critical at all as it's only needed for overlayfs on top
of fuse/virtiofs.

Choice of EINVAL is not random, we just simulate a standard
behavior when RENAME_WHITEOUT flag is not supported.

Cc: Christian Brauner <brauner@...nel.org>
Cc: Seth Forshee <sforshee@...nel.org>
Cc: Miklos Szeredi <miklos@...redi.hu>
Cc: Amir Goldstein <amir73il@...il.com>
Cc: Bernd Schubert <bschubert@....com>
Cc: <linux-fsdevel@...r.kernel.org>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
---
 fs/fuse/dir.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index c50f951596dd..0cd01f25251f 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1111,6 +1111,9 @@ static int fuse_rename2(struct mnt_idmap *idmap, struct inode *olddir,
 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
 		return -EINVAL;
 
+	if ((flags & RENAME_WHITEOUT) && (idmap != &nop_mnt_idmap))
+		return -EINVAL;
+
 	if (flags) {
 		if (fc->no_rename2 || fc->minor < 23)
 			return -EINVAL;
-- 
2.34.1