fs: use low-level mapping helpers

In a few places the vfs needs to interact with bare k{g,u}ids directly
instead of struct inode. These are just a few. In previous patches we
introduced low-level mapping helpers that are able to support
filesystems mounted an idmapping. This patch simply converts the places
to use these new helpers.

Link: https://lore.kernel.org/r/20211123114227.3124056-7-brauner@kernel.org (v1)
Link: https://lore.kernel.org/r/20211130121032.3753852-7-brauner@kernel.org (v2)
Link: https://lore.kernel.org/r/20211203111707.3901969-7-brauner@kernel.org
Cc: Seth Forshee <sforshee@digitalocean.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org
Reviewed-by: Seth Forshee <sforshee@digitalocean.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

4 files changed, 16 insertions, 26 deletions

diff --git a/fs/ksmbd/smbacl.c b/fs/ksmbd/smbacl.c
index ab8099e0fd7f..6ecf55ea1fed 100644
--- a/fs/ksmbd/smbacl.c
+++ b/fs/ksmbd/smbacl.c
@@ -275,14 +275,7 @@ static int sid_to_id(struct user_namespace *user_ns,
 		uid_t id;
 
 		id = le32_to_cpu(psid->sub_auth[psid->num_subauth - 1]);
-		/*
-		 * Translate raw sid into kuid in the server's user
-		 * namespace.
-		 */
-		uid = make_kuid(&init_user_ns, id);
-
-		/* If this is an idmapped mount, apply the idmapping. */
-		uid = kuid_from_mnt(user_ns, uid);
+		uid = mapped_kuid_user(user_ns, &init_user_ns, KUIDT_INIT(id));
 		if (uid_valid(uid)) {
 			fattr->cf_uid = uid;
 			rc = 0;
@@ -292,14 +285,7 @@ static int sid_to_id(struct user_namespace *user_ns,
 		gid_t id;
 
 		id = le32_to_cpu(psid->sub_auth[psid->num_subauth - 1]);
-		/*
-		 * Translate raw sid into kgid in the server's user
-		 * namespace.
-		 */
-		gid = make_kgid(&init_user_ns, id);
-
-		/* If this is an idmapped mount, apply the idmapping. */
-		gid = kgid_from_mnt(user_ns, gid);
+		gid = mapped_kgid_user(user_ns, &init_user_ns, KGIDT_INIT(id));
 		if (gid_valid(gid)) {
 			fattr->cf_gid = gid;
 			rc = 0;
diff --git a/fs/ksmbd/smbacl.h b/fs/ksmbd/smbacl.h
index eba1ebb9e92e..811af3309429 100644
--- a/fs/ksmbd/smbacl.h
+++ b/fs/ksmbd/smbacl.h
@@ -217,7 +217,7 @@ static inline uid_t posix_acl_uid_translate(struct user_namespace *mnt_userns,
 	kuid_t kuid;
 
 	/* If this is an idmapped mount, apply the idmapping. */
-	kuid = kuid_into_mnt(mnt_userns, pace->e_uid);
+	kuid = mapped_kuid_fs(mnt_userns, &init_user_ns, pace->e_uid);
 
 	/* Translate the kuid into a userspace id ksmbd would see. */
 	return from_kuid(&init_user_ns, kuid);
@@ -229,7 +229,7 @@ static inline gid_t posix_acl_gid_translate(struct user_namespace *mnt_userns,
 	kgid_t kgid;
 
 	/* If this is an idmapped mount, apply the idmapping. */
-	kgid = kgid_into_mnt(mnt_userns, pace->e_gid);
+	kgid = mapped_kgid_fs(mnt_userns, &init_user_ns, pace->e_gid);
 
 	/* Translate the kgid into a userspace id ksmbd would see. */
 	return from_kgid(&init_user_ns, kgid);
diff --git a/fs/open.c b/fs/open.c
index 2450cc1a2f64..40a00e71865b 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -653,8 +653,8 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
 	gid = make_kgid(current_user_ns(), group);
 
 	mnt_userns = mnt_user_ns(path->mnt);
-	uid = kuid_from_mnt(mnt_userns, uid);
-	gid = kgid_from_mnt(mnt_userns, gid);
+	uid = mapped_kuid_user(mnt_userns, &init_user_ns, uid);
+	gid = mapped_kgid_user(mnt_userns, &init_user_ns, gid);
 
 retry_deleg:
 	newattrs.ia_valid =  ATTR_CTIME;
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 632bfdcf7cc0..4b5fb9a9b90f 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -375,7 +375,9 @@ posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
                                         goto check_perm;
                                 break;
                         case ACL_USER:
-				uid = kuid_into_mnt(mnt_userns, pa->e_uid);
+				uid = mapped_kuid_fs(mnt_userns,
+						      &init_user_ns,
+						      pa->e_uid);
 				if (uid_eq(uid, current_fsuid()))
                                         goto mask;
 				break;
@@ -388,7 +390,9 @@ posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
                                 }
 				break;
                         case ACL_GROUP:
-				gid = kgid_into_mnt(mnt_userns, pa->e_gid);
+				gid = mapped_kgid_fs(mnt_userns,
+						      &init_user_ns,
+						      pa->e_gid);
 				if (in_group_p(gid)) {
 					found = 1;
 					if ((pa->e_perm & want) == want)
@@ -735,17 +739,17 @@ static void posix_acl_fix_xattr_userns(
 		case ACL_USER:
 			uid = make_kuid(from, le32_to_cpu(entry->e_id));
 			if (from_user)
-				uid = kuid_from_mnt(mnt_userns, uid);
+				uid = mapped_kuid_user(mnt_userns, &init_user_ns, uid);
 			else
-				uid = kuid_into_mnt(mnt_userns, uid);
+				uid = mapped_kuid_fs(mnt_userns, &init_user_ns, uid);
 			entry->e_id = cpu_to_le32(from_kuid(to, uid));
 			break;
 		case ACL_GROUP:
 			gid = make_kgid(from, le32_to_cpu(entry->e_id));
 			if (from_user)
-				gid = kgid_from_mnt(mnt_userns, gid);
+				gid = mapped_kgid_user(mnt_userns, &init_user_ns, gid);
 			else
-				gid = kgid_into_mnt(mnt_userns, gid);
+				gid = mapped_kgid_fs(mnt_userns, &init_user_ns, gid);
 			entry->e_id = cpu_to_le32(from_kgid(to, gid));
 			break;
 		default: