fs: port vfs_*() helpers to struct mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

1 files changed, 14 insertions, 9 deletions

diff --git a/fs/open.c b/fs/open.c
index 82c1a28b33089..60a81db586ef5 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -36,9 +36,10 @@
 
 #include "internal.h"
 
-int do_truncate(struct user_namespace *mnt_userns, struct dentry *dentry,
+int do_truncate(struct mnt_idmap *idmap, struct dentry *dentry,
 		loff_t length, unsigned int time_attrs, struct file *filp)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	int ret;
 	struct iattr newattrs;
 
@@ -62,13 +63,14 @@ int do_truncate(struct user_namespace *mnt_userns, struct dentry *dentry,
 
 	inode_lock(dentry->d_inode);
 	/* Note any delegations or leases have already been broken: */
-	ret = notify_change(mnt_userns, dentry, &newattrs, NULL);
+	ret = notify_change(idmap, dentry, &newattrs, NULL);
 	inode_unlock(dentry->d_inode);
 	return ret;
 }
 
 long vfs_truncate(const struct path *path, loff_t length)
 {
+	struct mnt_idmap *idmap;
 	struct user_namespace *mnt_userns;
 	struct inode *inode;
 	long error;
@@ -85,7 +87,8 @@ long vfs_truncate(const struct path *path, loff_t length)
 	if (error)
 		goto out;
 
-	mnt_userns = mnt_user_ns(path->mnt);
+	idmap = mnt_idmap(path->mnt);
+	mnt_userns = mnt_idmap_owner(idmap);
 	error = inode_permission(mnt_userns, inode, MAY_WRITE);
 	if (error)
 		goto mnt_drop_write_and_out;
@@ -108,7 +111,7 @@ long vfs_truncate(const struct path *path, loff_t length)
 
 	error = security_path_truncate(path);
 	if (!error)
-		error = do_truncate(mnt_userns, path->dentry, length, 0, NULL);
+		error = do_truncate(idmap, path->dentry, length, 0, NULL);
 
 put_write_and_out:
 	put_write_access(inode);
@@ -190,7 +193,7 @@ long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 	sb_start_write(inode->i_sb);
 	error = security_file_truncate(f.file);
 	if (!error)
-		error = do_truncate(file_mnt_user_ns(f.file), dentry, length,
+		error = do_truncate(file_mnt_idmap(f.file), dentry, length,
 				    ATTR_MTIME | ATTR_CTIME, f.file);
 	sb_end_write(inode->i_sb);
 out_putf:
@@ -603,7 +606,7 @@ retry_deleg:
 		goto out_unlock;
 	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
-	error = notify_change(mnt_user_ns(path->mnt), path->dentry,
+	error = notify_change(mnt_idmap(path->mnt), path->dentry,
 			      &newattrs, &delegated_inode);
 out_unlock:
 	inode_unlock(inode);
@@ -701,6 +704,7 @@ static inline bool setattr_vfsgid(struct iattr *attr, kgid_t kgid)
 
 int chown_common(const struct path *path, uid_t user, gid_t group)
 {
+	struct mnt_idmap *idmap;
 	struct user_namespace *mnt_userns, *fs_userns;
 	struct inode *inode = path->dentry->d_inode;
 	struct inode *delegated_inode = NULL;
@@ -712,7 +716,8 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
 	uid = make_kuid(current_user_ns(), user);
 	gid = make_kgid(current_user_ns(), group);
 
-	mnt_userns = mnt_user_ns(path->mnt);
+	idmap = mnt_idmap(path->mnt);
+	mnt_userns = mnt_idmap_owner(idmap);
 	fs_userns = i_user_ns(inode);
 
 retry_deleg:
@@ -733,7 +738,7 @@ retry_deleg:
 		from_vfsuid(mnt_userns, fs_userns, newattrs.ia_vfsuid),
 		from_vfsgid(mnt_userns, fs_userns, newattrs.ia_vfsgid));
 	if (!error)
-		error = notify_change(mnt_userns, path->dentry, &newattrs,
+		error = notify_change(idmap, path->dentry, &newattrs,
 				      &delegated_inode);
 	inode_unlock(inode);
 	if (delegated_inode) {
@@ -1064,7 +1069,7 @@ struct file *dentry_create(const struct path *path, int flags, umode_t mode,
 	if (IS_ERR(f))
 		return f;
 
-	error = vfs_create(mnt_user_ns(path->mnt),
+	error = vfs_create(mnt_idmap(path->mnt),
 			   d_inode(path->dentry->d_parent),
 			   path->dentry, mode, true);
 	if (!error)