fs: make helpers idmap mount aware

Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

1 files changed, 15 insertions, 16 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
index 508e9ea8e6f3..967aefda6ee3 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -27,8 +27,9 @@
 
 #include "internal.h"
 
-int simple_getattr(const struct path *path, struct kstat *stat,
-		   u32 request_mask, unsigned int query_flags)
+int simple_getattr(struct user_namespace *mnt_userns, const struct path *path,
+		   struct kstat *stat, u32 request_mask,
+		   unsigned int query_flags)
 {
 	struct inode *inode = d_inode(path->dentry);
 	generic_fillattr(&init_user_ns, inode, stat);
@@ -447,9 +448,9 @@ int simple_rmdir(struct inode *dir, struct dentry *dentry)
 }
 EXPORT_SYMBOL(simple_rmdir);
 
-int simple_rename(struct inode *old_dir, struct dentry *old_dentry,
-		  struct inode *new_dir, struct dentry *new_dentry,
-		  unsigned int flags)
+int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
+		  struct dentry *old_dentry, struct inode *new_dir,
+		  struct dentry *new_dentry, unsigned int flags)
 {
 	struct inode *inode = d_inode(old_dentry);
 	int they_are_dirs = d_is_dir(old_dentry);
@@ -492,18 +493,19 @@ EXPORT_SYMBOL(simple_rename);
  * on simple regular filesystems.  Anything that needs to change on-disk
  * or wire state on size changes needs its own setattr method.
  */
-int simple_setattr(struct dentry *dentry, struct iattr *iattr)
+int simple_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		   struct iattr *iattr)
 {
 	struct inode *inode = d_inode(dentry);
 	int error;
 
-	error = setattr_prepare(&init_user_ns, dentry, iattr);
+	error = setattr_prepare(mnt_userns, dentry, iattr);
 	if (error)
 		return error;
 
 	if (iattr->ia_valid & ATTR_SIZE)
 		truncate_setsize(inode, iattr->ia_size);
-	setattr_copy(&init_user_ns, inode, iattr);
+	setattr_copy(mnt_userns, inode, iattr);
 	mark_inode_dirty(inode);
 	return 0;
 }
@@ -1300,7 +1302,8 @@ static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry,
 	return ERR_PTR(-ENOENT);
 }
 
-static int empty_dir_getattr(const struct path *path, struct kstat *stat,
+static int empty_dir_getattr(struct user_namespace *mnt_userns,
+			     const struct path *path, struct kstat *stat,
 			     u32 request_mask, unsigned int query_flags)
 {
 	struct inode *inode = d_inode(path->dentry);
@@ -1308,7 +1311,8 @@ static int empty_dir_getattr(const struct path *path, struct kstat *stat,
 	return 0;
 }
 
-static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr)
+static int empty_dir_setattr(struct user_namespace *mnt_userns,
+			     struct dentry *dentry, struct iattr *attr)
 {
 	return -EPERM;
 }
@@ -1318,14 +1322,9 @@ static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t siz
 	return -EOPNOTSUPP;
 }
 
-static int empty_dir_permission(struct inode *inode, int mask)
-{
-	return generic_permission(&init_user_ns, inode, mask);
-}
-
 static const struct inode_operations empty_dir_inode_operations = {
 	.lookup		= empty_dir_lookup,
-	.permission	= empty_dir_permission,
+	.permission	= generic_permission,
 	.setattr	= empty_dir_setattr,
 	.getattr	= empty_dir_getattr,
 	.listxattr	= empty_dir_listxattr,