@@ -1,3 +1,3 @@
obj-$(CONFIG_FS_VERITY) += fsverity.o
-fsverity-y := hash_algs.o setup.o verify.o
+fsverity-y := hash_algs.o ioctl.o setup.o verify.o
new file mode 100644
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/verity/ioctl.c: fs-verity ioctls
+ *
+ * Copyright (C) 2018 Google LLC
+ *
+ * Originally written by Jaegeuk Kim and Michael Halcrow;
+ * heavily rewritten by Eric Biggers.
+ */
+
+#include "fsverity_private.h"
+
+#include <linux/capability.h>
+#include <linux/mm.h>
+#include <linux/mount.h>
+#include <linux/uaccess.h>
+
+/**
+ * fsverity_ioctl_enable - enable fs-verity on a file
+ *
+ * Set the verity bit on a file. Userspace must have already appended verity
+ * metadata to the file.
+ *
+ * Enabling fs-verity makes the file contents immutable, and the filesystem
+ * doesn't allow disabling it (other than by replacing the file).
+ *
+ * To avoid races with the file contents being modified, no processes must have
+ * the file open for writing. This includes the caller!
+ *
+ * Return: 0 on success, -errno on failure
+ */
+int fsverity_ioctl_enable(struct file *filp, const void __user *arg)
+{
+ struct inode *inode = file_inode(filp);
+ struct fsverity_info *vi;
+ int err;
+
+ /*
+ * In principle we need only check 'inode_owner_or_capable(inode)',
+ * which would allow non-root users to enable fs-verity on their own
+ * files. But to be conservative, for now restrict this to root-only.
+ */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EACCES;
+
+ if (arg) /* argument is reserved */
+ return -EINVAL;
+
+ if (S_ISDIR(inode->i_mode))
+ return -EISDIR;
+
+ if (!S_ISREG(inode->i_mode))
+ return -EINVAL;
+
+ err = mnt_want_write_file(filp);
+ if (err)
+ goto out;
+
+ /*
+ * Temporarily lock out writers via writable file descriptors or
+ * truncate(). This should stabilize the contents of the file as well
+ * as its size. Note that at the end of this ioctl we will unlock
+ * writers, but at that point the verity bit will be set (if the ioctl
+ * succeeded), preventing future writers.
+ */
+ err = deny_write_access(filp);
+ if (err) /* -ETXTBSY */
+ goto out_drop_write;
+
+ /*
+ * fsync so that the verity bit can't be persisted to disk prior to the
+ * data, causing verification errors after a crash.
+ */
+ err = vfs_fsync(filp, 1);
+ if (err)
+ goto out_allow_write;
+
+ /* Serialize concurrent use of this ioctl on the same inode */
+ inode_lock(inode);
+
+ if (get_fsverity_info(inode)) { /* fs-verity already enabled? */
+ err = -EEXIST;
+ goto out_unlock;
+ }
+
+ /* Validate the verity metadata */
+ vi = create_fsverity_info(inode, true);
+ if (IS_ERR(vi)) {
+ err = PTR_ERR(vi);
+ if (err == -EINVAL) /* distinguish "invalid metadata" case */
+ err = -EBADMSG;
+ goto out_unlock;
+ }
+
+ /* Set the verity bit */
+ err = inode->i_sb->s_vop->set_verity(inode, vi->data_i_size);
+ if (err)
+ goto out_free_vi;
+
+ /* Invalidate all cached pages, forcing re-verification */
+ truncate_inode_pages(inode->i_mapping, 0);
+
+ /*
+ * Set ->i_verity_info, unless another task managed to do it already
+ * between ->set_verity() and here.
+ */
+ if (set_fsverity_info(inode, vi))
+ vi = NULL;
+ err = 0;
+out_free_vi:
+ free_fsverity_info(vi);
+out_unlock:
+ inode_unlock(inode);
+out_allow_write:
+ allow_write_access(filp);
+out_drop_write:
+ mnt_drop_write_file(filp);
+out:
+ return err;
+}
+EXPORT_SYMBOL_GPL(fsverity_ioctl_enable);
@@ -21,6 +21,9 @@ struct fsverity_operations {
#if __FS_HAS_VERITY
+/* ioctl.c */
+extern int fsverity_ioctl_enable(struct file *filp, const void __user *arg);
+
/* setup.c */
extern int fsverity_file_open(struct inode *inode, struct file *filp);
extern int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr);
@@ -35,6 +38,14 @@ extern void fsverity_enqueue_verify_work(struct work_struct *work);
#else /* !__FS_HAS_VERITY */
+/* ioctl.c */
+
+static inline int fsverity_ioctl_enable(struct file *filp,
+ const void __user *arg)
+{
+ return -EOPNOTSUPP;
+}
+
/* setup.c */
static inline int fsverity_file_open(struct inode *inode, struct file *filp)