fs: port vfs{g,u}id helpers to 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, 6 insertions, 11 deletions

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 7e0a8a068f98..8cc52110f1f9 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -377,7 +377,6 @@ posix_acl_permission(struct mnt_idmap *idmap, struct inode *inode,
 {
 	const struct posix_acl_entry *pa, *pe, *mask_obj;
 	struct user_namespace *fs_userns = i_user_ns(inode);
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	int found = 0;
 	vfsuid_t vfsuid;
 	vfsgid_t vfsgid;
@@ -393,7 +392,7 @@ posix_acl_permission(struct mnt_idmap *idmap, struct inode *inode,
                                         goto check_perm;
                                 break;
                         case ACL_USER:
-				vfsuid = make_vfsuid(mnt_userns, fs_userns,
+				vfsuid = make_vfsuid(idmap, fs_userns,
 						     pa->e_uid);
 				if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
                                         goto mask;
@@ -407,7 +406,7 @@ posix_acl_permission(struct mnt_idmap *idmap, struct inode *inode,
                                 }
 				break;
                         case ACL_GROUP:
-				vfsgid = make_vfsgid(mnt_userns, fs_userns,
+				vfsgid = make_vfsgid(idmap, fs_userns,
 						     pa->e_gid);
 				if (vfsgid_in_group_p(vfsgid)) {
 					found = 1;
@@ -894,7 +893,6 @@ static ssize_t vfs_posix_acl_to_xattr(struct mnt_idmap *idmap,
 	struct posix_acl_xattr_header *ext_acl = buffer;
 	struct posix_acl_xattr_entry *ext_entry;
 	struct user_namespace *fs_userns, *caller_userns;
-	struct user_namespace *mnt_userns;
 	ssize_t real_size, n;
 	vfsuid_t vfsuid;
 	vfsgid_t vfsgid;
@@ -910,19 +908,18 @@ static ssize_t vfs_posix_acl_to_xattr(struct mnt_idmap *idmap,
 
 	fs_userns = i_user_ns(inode);
 	caller_userns = current_user_ns();
-	mnt_userns = mnt_idmap_owner(idmap);
 	for (n=0; n < acl->a_count; n++, ext_entry++) {
 		const struct posix_acl_entry *acl_e = &acl->a_entries[n];
 		ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
 		ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
 		switch(acl_e->e_tag) {
 		case ACL_USER:
-			vfsuid = make_vfsuid(mnt_userns, fs_userns, acl_e->e_uid);
+			vfsuid = make_vfsuid(idmap, fs_userns, acl_e->e_uid);
 			ext_entry->e_id = cpu_to_le32(from_kuid(
 				caller_userns, vfsuid_into_kuid(vfsuid)));
 			break;
 		case ACL_GROUP:
-			vfsgid = make_vfsgid(mnt_userns, fs_userns, acl_e->e_gid);
+			vfsgid = make_vfsgid(idmap, fs_userns, acl_e->e_gid);
 			ext_entry->e_id = cpu_to_le32(from_kgid(
 				caller_userns, vfsgid_into_kgid(vfsgid)));
 			break;
@@ -1022,18 +1019,16 @@ static int vfs_set_acl_idmapped_mnt(struct mnt_idmap *idmap,
 				    struct user_namespace *fs_userns,
 				    struct posix_acl *acl)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-
 	for (int n = 0; n < acl->a_count; n++) {
 		struct posix_acl_entry *acl_e = &acl->a_entries[n];
 
 		switch (acl_e->e_tag) {
 		case ACL_USER:
-			acl_e->e_uid = from_vfsuid(mnt_userns, fs_userns,
+			acl_e->e_uid = from_vfsuid(idmap, fs_userns,
 						   VFSUIDT_INIT(acl_e->e_uid));
 			break;
 		case ACL_GROUP:
-			acl_e->e_gid = from_vfsgid(mnt_userns, fs_userns,
+			acl_e->e_gid = from_vfsgid(idmap, fs_userns,
 						   VFSGIDT_INIT(acl_e->e_gid));
 			break;
 		}