[PATCH v3 09/11] fs/fuse: properly handle idmapped ->rename op

[Alexander Mikhalitsyn]

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@xxxxxxxxxx>
Cc: Seth Forshee <sforshee@xxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Amir Goldstein <amir73il@xxxxxxxxx>
Cc: Bernd Schubert <bschubert@xxxxxxx>
Cc: <linux-fsdevel@xxxxxxxxxxxxxxx>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
---
v2:
	- this commit added
---
 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