fs: port ->setattr() to pass 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>

2 files changed, 7 insertions, 6 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index a415c02ede39..e38bd3a49f46 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -398,7 +398,7 @@ extern long fat_generic_ioctl(struct file *filp, unsigned int cmd,
 			      unsigned long arg);
 extern const struct file_operations fat_file_operations;
 extern const struct inode_operations fat_file_inode_operations;
-extern int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+extern int fat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		       struct iattr *attr);
 extern void fat_truncate_blocks(struct inode *inode, loff_t offset);
 extern int fat_getattr(struct user_namespace *mnt_userns,
diff --git a/fs/fat/file.c b/fs/fat/file.c
index 8a6b493b5b5f..b762109a964f 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -90,13 +90,13 @@ static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
 	 * out the RO attribute for checking by the security
 	 * module, just because it maps to a file mode.
 	 */
-	err = security_inode_setattr(file_mnt_user_ns(file),
+	err = security_inode_setattr(file_mnt_idmap(file),
 				     file->f_path.dentry, &ia);
 	if (err)
 		goto out_unlock_inode;
 
 	/* This MUST be done before doing anything irreversible... */
-	err = fat_setattr(file_mnt_user_ns(file), file->f_path.dentry, &ia);
+	err = fat_setattr(file_mnt_idmap(file), file->f_path.dentry, &ia);
 	if (err)
 		goto out_unlock_inode;
 
@@ -477,9 +477,10 @@ static int fat_allow_set_time(struct user_namespace *mnt_userns,
 /* valid file mode bits */
 #define FAT_VALID_MODE	(S_IFREG | S_IFDIR | S_IRWXUGO)
 
-int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+int fat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		struct iattr *attr)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 	struct inode *inode = d_inode(dentry);
 	unsigned int ia_valid;
@@ -492,7 +493,7 @@ int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 			attr->ia_valid &= ~TIMES_SET_FLAGS;
 	}
 
-	error = setattr_prepare(mnt_userns, dentry, attr);
+	error = setattr_prepare(idmap, dentry, attr);
 	attr->ia_valid = ia_valid;
 	if (error) {
 		if (sbi->options.quiet)
@@ -564,7 +565,7 @@ int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 		fat_truncate_time(inode, &attr->ia_mtime, S_MTIME);
 	attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
 
-	setattr_copy(mnt_userns, inode, attr);
+	setattr_copy(idmap, inode, attr);
 	mark_inode_dirty(inode);
 out:
 	return error;