xfs: add fs-verity support

Add integration with fs-verity. The XFS store fs-verity metadata in
the extended attributes. The metadata consist of verity descriptor
and Merkle tree blocks.

The descriptor is stored under "verity_descriptor" extended
attribute. The Merkle tree blocks are stored under binary indexes.

When fs-verity is enabled on an inode, the XFS_IVERITY_CONSTRUCTION
flag is set meaning that the Merkle tree is being build. The
initialization ends with storing of verity descriptor and setting
inode on-disk flag (XFS_DIFLAG2_VERITY).

The verification on read is done in iomap. Based on the inode verity
flag the IOMAP_F_READ_VERITY is set in xfs_read_iomap_begin() to let
iomap know that verification is needed.

Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>

fs/xfs/Makefile

@@ -130,6 +130,7 @@ xfs-$(CONFIG_XFS_POSIX_ACL)	+= xfs_acl.o
 xfs-$(CONFIG_SYSCTL)		+= xfs_sysctl.o
 xfs-$(CONFIG_COMPAT)		+= xfs_ioctl32.o
 xfs-$(CONFIG_EXPORTFS_BLOCK_OPS)	+= xfs_pnfs.o
+xfs-$(CONFIG_FS_VERITY)		+= xfs_verity.o
 
 # notify failure
 ifeq ($(CONFIG_MEMORY_FAILURE),y)

fs/xfs/libxfs/xfs_attr.c

@@ -26,6 +26,7 @@
 #include "xfs_trace.h"
 #include "xfs_attr_item.h"
 #include "xfs_xattr.h"
+#include "xfs_verity.h"
 
 struct kmem_cache		*xfs_attr_intent_cache;
 
@@ -1635,6 +1636,18 @@ xfs_attr_namecheck(
 		return xfs_verify_pptr(mp, (struct xfs_parent_name_rec *)name);
 	}
 
+	if (flags & XFS_ATTR_VERITY) {
+		/* Merkle tree pages are stored under u64 indexes */
+		if (length == sizeof(__be64))
+			return true;
+
+		/* Verity descriptor blocks are held in a named attribute. */
+		if (length == XFS_VERITY_DESCRIPTOR_NAME_LEN)
+			return true;
+
+		return false;
+	}
+
 	return xfs_str_attr_namecheck(name, length);
 }
 

fs/xfs/xfs_inode.h

@@ -324,7 +324,8 @@ static inline bool xfs_inode_has_large_extent_counts(struct xfs_inode *ip)
  * inactivation completes, both flags will be cleared and the inode is a
  * plain old IRECLAIMABLE inode.
  */
-#define XFS_INACTIVATING	(1 << 13)
+#define XFS_INACTIVATING		(1 << 13)
+#define XFS_IVERITY_CONSTRUCTION	(1 << 14) /* merkle tree construction */
 
 /* All inode state flags related to inode reclaim. */
 #define XFS_ALL_IRECLAIM_FLAGS	(XFS_IRECLAIMABLE | \

fs/xfs/xfs_iomap.c

@@ -143,6 +143,9 @@ xfs_bmbt_to_iomap(
 	    (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
 		iomap->flags |= IOMAP_F_DIRTY;
 
+	if (fsverity_active(VFS_I(ip)))
+		iomap->flags |= IOMAP_F_READ_VERITY;
+
 	iomap->validity_cookie = sequence_cookie;
 	iomap->folio_ops = &xfs_iomap_folio_ops;
 	return 0;

fs/xfs/xfs_ondisk.h

@@ -189,6 +189,10 @@ xfs_check_ondisk_structs(void)
 	XFS_CHECK_VALUE(XFS_DQ_BIGTIME_EXPIRY_MIN << XFS_DQ_BIGTIME_SHIFT, 4);
 	XFS_CHECK_VALUE(XFS_DQ_BIGTIME_EXPIRY_MAX << XFS_DQ_BIGTIME_SHIFT,
 			16299260424LL);
+
+	/* fs-verity descriptor xattr name */
+	XFS_CHECK_VALUE(strlen(XFS_VERITY_DESCRIPTOR_NAME),
+			XFS_VERITY_DESCRIPTOR_NAME_LEN);
 }
 
 #endif /* __XFS_ONDISK_H */

fs/xfs/xfs_super.c

@@ -30,6 +30,7 @@
 #include "xfs_filestream.h"
 #include "xfs_quota.h"
 #include "xfs_sysfs.h"
+#include "xfs_verity.h"
 #include "xfs_ondisk.h"
 #include "xfs_rmap_item.h"
 #include "xfs_refcount_item.h"
@@ -1489,6 +1490,9 @@ xfs_fs_fill_super(
 	sb->s_quota_types = QTYPE_MASK_USR | QTYPE_MASK_GRP | QTYPE_MASK_PRJ;
 #endif
 	sb->s_op = &xfs_super_operations;
+#ifdef CONFIG_FS_VERITY
+	sb->s_vop = &xfs_verity_ops;
+#endif
 
 	/*
 	 * Delay mount work if the debug hook is set. This is debug
@@ -1685,6 +1689,10 @@ xfs_fs_fill_super(
 		xfs_warn(mp,
 	"EXPERIMENTAL Large extent counts feature in use. Use at your own risk!");
 
+	if (xfs_has_verity(mp))
+		xfs_alert(mp,
+	"EXPERIMENTAL fs-verity feature in use. Use at your own risk!");
+
 	error = xfs_mountfs(mp);
 	if (error)
 		goto out_filestream_unmount;

fs/xfs/xfs_verity.c

@@ -0,0 +1,214 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Red Hat, Inc.
+ */
+#include "xfs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_da_format.h"
+#include "xfs_da_btree.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_inode.h"
+#include "xfs_attr.h"
+#include "xfs_verity.h"
+#include "xfs_bmap_util.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+
+static int
+xfs_get_verity_descriptor(
+	struct inode		*inode,
+	void			*buf,
+	size_t			buf_size)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+	int			error = 0;
+	struct xfs_da_args	args = {
+		.dp		= ip,
+		.attr_filter	= XFS_ATTR_VERITY,
+		.name		= (const uint8_t *)XFS_VERITY_DESCRIPTOR_NAME,
+		.namelen	= XFS_VERITY_DESCRIPTOR_NAME_LEN,
+		.value		= buf,
+		.valuelen	= buf_size,
+	};
+
+	/*
+	 * The fact that (returned attribute size) == (provided buf_size) is
+	 * checked by xfs_attr_copy_value() (returns -ERANGE)
+	 */
+	error = xfs_attr_get(&args);
+	if (error)
+		return error;
+
+	return args.valuelen;
+}
+
+static int
+xfs_begin_enable_verity(
+	struct file	    *filp)
+{
+	struct inode	    *inode = file_inode(filp);
+	struct xfs_inode    *ip = XFS_I(inode);
+	int		    error = 0;
+
+	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
+
+	if (IS_DAX(inode))
+		return -EINVAL;
+
+	if (xfs_iflags_test(ip, XFS_IVERITY_CONSTRUCTION))
+		return -EBUSY;
+	xfs_iflags_set(ip, XFS_IVERITY_CONSTRUCTION);
+
+	return error;
+}
+
+static int
+xfs_end_enable_verity(
+	struct file		*filp,
+	const void		*desc,
+	size_t			desc_size,
+	u64			merkle_tree_size)
+{
+	struct inode		*inode = file_inode(filp);
+	struct xfs_inode	*ip = XFS_I(inode);
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_trans	*tp;
+	struct xfs_da_args	args = {
+		.dp		= ip,
+		.whichfork	= XFS_ATTR_FORK,
+		.attr_filter	= XFS_ATTR_VERITY,
+		.attr_flags	= XATTR_CREATE,
+		.name		= (const uint8_t *)XFS_VERITY_DESCRIPTOR_NAME,
+		.namelen	= XFS_VERITY_DESCRIPTOR_NAME_LEN,
+		.value		= (void *)desc,
+		.valuelen	= desc_size,
+	};
+	int			error = 0;
+
+	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
+
+	/* fs-verity failed, just cleanup */
+	if (desc == NULL)
+		goto out;
+
+	error = xfs_attr_set(&args);
+	if (error)
+		goto out;
+
+	/* Set fsverity inode flag */
+	error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_ichange,
+			0, 0, false, &tp);
+	if (error)
+		goto out;
+
+	/*
+	 * Ensure that we've persisted the verity information before we enable
+	 * it on the inode and tell the caller we have sealed the inode.
+	 */
+	ip->i_diflags2 |= XFS_DIFLAG2_VERITY;
+
+	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+	xfs_trans_set_sync(tp);
+
+	error = xfs_trans_commit(tp);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+	if (!error)
+		inode->i_flags |= S_VERITY;
+
+out:
+	xfs_iflags_clear(ip, XFS_IVERITY_CONSTRUCTION);
+	return error;
+}
+
+static struct page *
+xfs_read_merkle_tree_page(
+	struct inode		*inode,
+	pgoff_t			index,
+	unsigned long		num_ra_pages,
+	u8			log_blocksize)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+	struct page		*page = NULL;
+	__be64			name = cpu_to_be64(index << PAGE_SHIFT);
+	uint32_t		bs = 1 << log_blocksize;
+	struct xfs_da_args	args = {
+		.dp		= ip,
+		.attr_filter	= XFS_ATTR_VERITY,
+		.op_flags	= XFS_DA_OP_BUFFER,
+		.name		= (const uint8_t *)&name,
+		.namelen	= sizeof(__be64),
+		.valuelen	= bs,
+	};
+	int			error = 0;
+
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return ERR_PTR(-ENOMEM);
+
+	error = xfs_attr_get(&args);
+	if (error) {
+		kmem_free(args.value);
+		xfs_buf_rele(args.bp);
+		put_page(page);
+		return ERR_PTR(-EFAULT);
+	}
+
+	if (args.bp->b_flags & XBF_VERITY_CHECKED)
+		SetPageChecked(page);
+
+	page->private = (unsigned long)args.bp;
+	memcpy(page_address(page), args.value, args.valuelen);
+
+	kmem_free(args.value);
+	return page;
+}
+
+static int
+xfs_write_merkle_tree_block(
+	struct inode		*inode,
+	const void		*buf,
+	u64			pos,
+	unsigned int		size)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+	__be64			name = cpu_to_be64(pos);
+	struct xfs_da_args	args = {
+		.dp		= ip,
+		.whichfork	= XFS_ATTR_FORK,
+		.attr_filter	= XFS_ATTR_VERITY,
+		.attr_flags	= XATTR_CREATE,
+		.name		= (const uint8_t *)&name,
+		.namelen	= sizeof(__be64),
+		.value		= (void *)buf,
+		.valuelen	= size,
+	};
+
+	return xfs_attr_set(&args);
+}
+
+static void
+xfs_drop_page(
+	struct page	*page)
+{
+	struct xfs_buf *buf = (struct xfs_buf *)page->private;
+
+	ASSERT(buf != NULL);
+
+	if (PageChecked(page))
+		buf->b_flags |= XBF_VERITY_CHECKED;
+
+	xfs_buf_rele(buf);
+	put_page(page);
+}
+
+const struct fsverity_operations xfs_verity_ops = {
+	.begin_enable_verity = &xfs_begin_enable_verity,
+	.end_enable_verity = &xfs_end_enable_verity,
+	.get_verity_descriptor = &xfs_get_verity_descriptor,
+	.read_merkle_tree_page = &xfs_read_merkle_tree_page,
+	.write_merkle_tree_block = &xfs_write_merkle_tree_block,
+	.drop_page = &xfs_drop_page,
+};

fs/xfs/xfs_verity.h

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Red Hat, Inc.
+ */
+#ifndef __XFS_VERITY_H__
+#define __XFS_VERITY_H__
+
+#include <linux/fsverity.h>
+
+#define XFS_VERITY_DESCRIPTOR_NAME "verity_descriptor"
+#define XFS_VERITY_DESCRIPTOR_NAME_LEN 17
+
+#ifdef CONFIG_FS_VERITY
+extern const struct fsverity_operations xfs_verity_ops;
+#else
+#define xfs_verity_ops NULL
+#endif	/* CONFIG_FS_VERITY */
+
+#endif	/* __XFS_VERITY_H__ */