fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap

Convert to struct mnt_idmap.
Remove legacy file_mnt_user_ns() and mnt_user_ns().

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, 7 insertions, 9 deletions

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index c6728a629437..d6cc4812ca53 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -227,8 +227,7 @@ static int common_perm(const char *op, const struct path *path, u32 mask,
  */
 static int common_perm_cond(const char *op, const struct path *path, u32 mask)
 {
-	struct user_namespace *mnt_userns = mnt_user_ns(path->mnt);
-	vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns,
+	vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_idmap(path->mnt),
 					    d_backing_inode(path->dentry));
 	struct path_cond cond = {
 		vfsuid_into_kuid(vfsuid),
@@ -273,14 +272,13 @@ static int common_perm_rm(const char *op, const struct path *dir,
 			  struct dentry *dentry, u32 mask)
 {
 	struct inode *inode = d_backing_inode(dentry);
-	struct user_namespace *mnt_userns = mnt_user_ns(dir->mnt);
 	struct path_cond cond = { };
 	vfsuid_t vfsuid;
 
 	if (!inode || !path_mediated_fs(dentry))
 		return 0;
 
-	vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+	vfsuid = i_uid_into_vfsuid(mnt_idmap(dir->mnt), inode);
 	cond.uid = vfsuid_into_kuid(vfsuid);
 	cond.mode = inode->i_mode;
 
@@ -379,7 +377,7 @@ static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_d
 
 	label = begin_current_label_crit_section();
 	if (!unconfined(label)) {
-		struct user_namespace *mnt_userns = mnt_user_ns(old_dir->mnt);
+		struct mnt_idmap *idmap = mnt_idmap(old_dir->mnt);
 		vfsuid_t vfsuid;
 		struct path old_path = { .mnt = old_dir->mnt,
 					 .dentry = old_dentry };
@@ -388,14 +386,14 @@ static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_d
 		struct path_cond cond = {
 			.mode = d_backing_inode(old_dentry)->i_mode
 		};
-		vfsuid = i_uid_into_vfsuid(mnt_userns, d_backing_inode(old_dentry));
+		vfsuid = i_uid_into_vfsuid(idmap, d_backing_inode(old_dentry));
 		cond.uid = vfsuid_into_kuid(vfsuid);
 
 		if (flags & RENAME_EXCHANGE) {
 			struct path_cond cond_exchange = {
 				.mode = d_backing_inode(new_dentry)->i_mode,
 			};
-			vfsuid = i_uid_into_vfsuid(mnt_userns, d_backing_inode(old_dentry));
+			vfsuid = i_uid_into_vfsuid(idmap, d_backing_inode(old_dentry));
 			cond_exchange.uid = vfsuid_into_kuid(vfsuid);
 
 			error = aa_path_perm(OP_RENAME_SRC, label, &new_path, 0,
@@ -460,13 +458,13 @@ static int apparmor_file_open(struct file *file)
 
 	label = aa_get_newest_cred_label(file->f_cred);
 	if (!unconfined(label)) {
-		struct user_namespace *mnt_userns = file_mnt_user_ns(file);
+		struct mnt_idmap *idmap = file_mnt_idmap(file);
 		struct inode *inode = file_inode(file);
 		vfsuid_t vfsuid;
 		struct path_cond cond = {
 			.mode = inode->i_mode,
 		};
-		vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
+		vfsuid = i_uid_into_vfsuid(idmap, inode);
 		cond.uid = vfsuid_into_kuid(vfsuid);
 
 		error = aa_path_perm(OP_OPEN, label, &file->f_path, 0,