ksmbd: fix translation in ksmbd_acls_fattr()

When creating new filesystem objects ksmbd translates between k*ids and
s*ids. For this it often uses struct smb_fattr and stashes the k*ids in
cf_uid and cf_gid. Let cf_uid and cf_gid always contain the final
information taking any potential idmapped mounts into account. When
finally translation cf_*id into s*ids translate them into the user
namespace of ksmbd since that is the relevant user namespace here.

Cc: Steve French <stfrench@microsoft.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Hyunchul Lee <hyc.lee@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/smb2pdu.c

@@ -2381,10 +2381,12 @@ static int smb2_create_sd_buffer(struct ksmbd_work *work,
 			    le32_to_cpu(sd_buf->ccontext.DataLength), true);
 }
 
-static void ksmbd_acls_fattr(struct smb_fattr *fattr, struct inode *inode)
+static void ksmbd_acls_fattr(struct smb_fattr *fattr,
+			     struct user_namespace *mnt_userns,
+			     struct inode *inode)
 {
-	fattr->cf_uid = inode->i_uid;
-	fattr->cf_gid = inode->i_gid;
+	fattr->cf_uid = i_uid_into_mnt(mnt_userns, inode);
+	fattr->cf_gid = i_gid_into_mnt(mnt_userns, inode);
 	fattr->cf_mode = inode->i_mode;
 	fattr->cf_acls = NULL;
 	fattr->cf_dacls = NULL;
@@ -2893,7 +2895,7 @@ int smb2_open(struct ksmbd_work *work)
 					struct smb_ntsd *pntsd;
 					int pntsd_size, ace_num = 0;
 
-					ksmbd_acls_fattr(&fattr, inode);
+					ksmbd_acls_fattr(&fattr, user_ns, inode);
 					if (fattr.cf_acls)
 						ace_num = fattr.cf_acls->a_count;
 					if (fattr.cf_dacls)
@@ -5006,7 +5008,7 @@ static int smb2_get_info_sec(struct ksmbd_work *work,
 
 	user_ns = file_mnt_user_ns(fp->filp);
 	inode = file_inode(fp->filp);
-	ksmbd_acls_fattr(&fattr, inode);
+	ksmbd_acls_fattr(&fattr, user_ns, inode);
 
 	if (test_share_config_flag(work->tcon->share_conf,
 				   KSMBD_SHARE_FLAG_ACL_XATTR))

fs/ksmbd/smbacl.c

@@ -723,7 +723,7 @@ static void set_mode_dacl(struct user_namespace *user_ns,
 	}
 
 	/* owner RID */
-	uid = from_kuid(user_ns, fattr->cf_uid);
+	uid = from_kuid(&init_user_ns, fattr->cf_uid);
 	if (uid)
 		sid = &server_conf.domain_sid;
 	else
@@ -739,7 +739,7 @@ static void set_mode_dacl(struct user_namespace *user_ns,
 	ace_size = fill_ace_for_sid(pace, &sid_unix_groups,
 				    ACCESS_ALLOWED, 0, fattr->cf_mode, 0070);
 	pace->sid.sub_auth[pace->sid.num_subauth++] =
-		cpu_to_le32(from_kgid(user_ns, fattr->cf_gid));
+		cpu_to_le32(from_kgid(&init_user_ns, fattr->cf_gid));
 	pace->size = cpu_to_le16(ace_size + 4);
 	size += le16_to_cpu(pace->size);
 	pace = (struct smb_ace *)((char *)pndace + size);
@@ -880,7 +880,7 @@ int build_sec_desc(struct user_namespace *user_ns,
 	if (!nowner_sid_ptr)
 		return -ENOMEM;
 
-	uid = from_kuid(user_ns, fattr->cf_uid);
+	uid = from_kuid(&init_user_ns, fattr->cf_uid);
 	if (!uid)
 		sid_type = SIDUNIX_USER;
 	id_to_sid(uid, sid_type, nowner_sid_ptr);
@@ -891,7 +891,7 @@ int build_sec_desc(struct user_namespace *user_ns,
 		return -ENOMEM;
 	}
 
-	gid = from_kgid(user_ns, fattr->cf_gid);
+	gid = from_kgid(&init_user_ns, fattr->cf_gid);
 	id_to_sid(gid, SIDUNIX_GROUP, ngroup_sid_ptr);
 
 	offset = sizeof(struct smb_ntsd);