ovl: handle idmapped mounts in ovl_create_object() and ovl_tmpfile()

In preparation for allowing the overlay mount itself to be idmapped,
thread the mount's struct mnt_idmap into the inode creation path and
use it for inode_init_owner() instead of the hardcoded &nop_mnt_idmap.

The preallocated overlay inode's i_{u,g}id are copied into the override
credentials by ovl_override_creator_creds() to create the real upper
inode, so honoring the overlay mount idmap here makes newly created
files, directories, special files, symlinks and tmpfiles get the
caller's mapped fs{u,g}id once overlay mounts can be idmapped.

No functional change: until FS_ALLOW_IDMAP is set on ovl_fs_type the
overlay mount idmap is always &nop_mnt_idmap, so inode_init_owner()
behaves exactly as before.

Link: https://patch.msgid.link/20260615-work-idmapped-overlayfs-v1-1-7381632aa402@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index a033743dbf51..a7a393b04277 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -689,8 +689,8 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
 	return err;
 }
 
-static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
-			     const char *link)
+static int ovl_create_object(struct mnt_idmap *idmap, struct dentry *dentry,
+			     int mode, dev_t rdev, const char *link)
 {
 	int err;
 	struct inode *inode;
@@ -717,7 +717,7 @@ static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 	inode_state_set(inode, I_CREATING);
 	spin_unlock(&inode->i_lock);
 
-	inode_init_owner(&nop_mnt_idmap, inode, dentry->d_parent->d_inode, mode);
+	inode_init_owner(idmap, inode, dentry->d_parent->d_inode, mode);
 	attr.mode = inode->i_mode;
 
 	err = ovl_create_or_link(dentry, inode, &attr, false);
@@ -734,13 +734,13 @@ out:
 static int ovl_create(struct mnt_idmap *idmap, struct inode *dir,
 		      struct dentry *dentry, umode_t mode, bool excl)
 {
-	return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
+	return ovl_create_object(idmap, dentry, (mode & 07777) | S_IFREG, 0, NULL);
 }
 
 static struct dentry *ovl_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 				struct dentry *dentry, umode_t mode)
 {
-	return ERR_PTR(ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL));
+	return ERR_PTR(ovl_create_object(idmap, dentry, (mode & 07777) | S_IFDIR, 0, NULL));
 }
 
 static int ovl_mknod(struct mnt_idmap *idmap, struct inode *dir,
@@ -750,13 +750,13 @@ static int ovl_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
 		return -EPERM;
 
-	return ovl_create_object(dentry, mode, rdev, NULL);
+	return ovl_create_object(idmap, dentry, mode, rdev, NULL);
 }
 
 static int ovl_symlink(struct mnt_idmap *idmap, struct inode *dir,
 		       struct dentry *dentry, const char *link)
 {
-	return ovl_create_object(dentry, S_IFLNK, 0, link);
+	return ovl_create_object(idmap, dentry, S_IFLNK, 0, link);
 }
 
 static int ovl_set_link_redirect(struct dentry *dentry)
@@ -1444,7 +1444,7 @@ static int ovl_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
 	if (!inode)
 		goto drop_write;
 
-	inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
+	inode_init_owner(idmap, inode, dir, mode);
 	err = ovl_create_tmpfile(file, dentry, inode, inode->i_mode);
 	if (err)
 		goto put_inode;