Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 397 insertions, 0 deletions

diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
new file mode 100644
index 0000000000..2f37e1ea39
--- /dev/null
+++ b/fs/ext4/verity.c
@@ -0,0 +1,397 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/ext4/verity.c: fs-verity support for ext4
+ *
+ * Copyright 2019 Google LLC
+ */
+
+/*
+ * Implementation of fsverity_operations for ext4.
+ *
+ * ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past
+ * the end of the file, starting at the first 64K boundary beyond i_size.  This
+ * approach works because (a) verity files are readonly, and (b) pages fully
+ * beyond i_size aren't visible to userspace but can be read/written internally
+ * by ext4 with only some relatively small changes to ext4.  This approach
+ * avoids having to depend on the EA_INODE feature and on rearchitecturing
+ * ext4's xattr support to support paging multi-gigabyte xattrs into memory, and
+ * to support encrypting xattrs.  Note that the verity metadata *must* be
+ * encrypted when the file is, since it contains hashes of the plaintext data.
+ *
+ * Using a 64K boundary rather than a 4K one keeps things ready for
+ * architectures with 64K pages, and it doesn't necessarily waste space on-disk
+ * since there can be a hole between i_size and the start of the Merkle tree.
+ */
+
+#include <linux/quotaops.h>
+
+#include "ext4.h"
+#include "ext4_extents.h"
+#include "ext4_jbd2.h"
+
+static inline loff_t ext4_verity_metadata_pos(const struct inode *inode)
+{
+	return round_up(inode->i_size, 65536);
+}
+
+/*
+ * Read some verity metadata from the inode.  __vfs_read() can't be used because
+ * we need to read beyond i_size.
+ */
+static int pagecache_read(struct inode *inode, void *buf, size_t count,
+			  loff_t pos)
+{
+	while (count) {
+		struct folio *folio;
+		size_t n;
+
+		folio = read_mapping_folio(inode->i_mapping, pos >> PAGE_SHIFT,
+					 NULL);
+		if (IS_ERR(folio))
+			return PTR_ERR(folio);
+
+		n = memcpy_from_file_folio(buf, folio, pos, count);
+		folio_put(folio);
+
+		buf += n;
+		pos += n;
+		count -= n;
+	}
+	return 0;
+}
+
+/*
+ * Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
+ * kernel_write() can't be used because the file descriptor is readonly.
+ */
+static int pagecache_write(struct inode *inode, const void *buf, size_t count,
+			   loff_t pos)
+{
+	struct address_space *mapping = inode->i_mapping;
+	const struct address_space_operations *aops = mapping->a_ops;
+
+	if (pos + count > inode->i_sb->s_maxbytes)
+		return -EFBIG;
+
+	while (count) {
+		size_t n = min_t(size_t, count,
+				 PAGE_SIZE - offset_in_page(pos));
+		struct page *page;
+		void *fsdata = NULL;
+		int res;
+
+		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
+		if (res)
+			return res;
+
+		memcpy_to_page(page, offset_in_page(pos), buf, n);
+
+		res = aops->write_end(NULL, mapping, pos, n, n, page, fsdata);
+		if (res < 0)
+			return res;
+		if (res != n)
+			return -EIO;
+
+		buf += n;
+		pos += n;
+		count -= n;
+	}
+	return 0;
+}
+
+static int ext4_begin_enable_verity(struct file *filp)
+{
+	struct inode *inode = file_inode(filp);
+	const int credits = 2; /* superblock and inode for ext4_orphan_add() */
+	handle_t *handle;
+	int err;
+
+	if (IS_DAX(inode) || ext4_test_inode_flag(inode, EXT4_INODE_DAX))
+		return -EINVAL;
+
+	if (ext4_verity_in_progress(inode))
+		return -EBUSY;
+
+	/*
+	 * Since the file was opened readonly, we have to initialize the jbd
+	 * inode and quotas here and not rely on ->open() doing it.  This must
+	 * be done before evicting the inline data.
+	 */
+
+	err = ext4_inode_attach_jinode(inode);
+	if (err)
+		return err;
+
+	err = dquot_initialize(inode);
+	if (err)
+		return err;
+
+	err = ext4_convert_inline_data(inode);
+	if (err)
+		return err;
+
+	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
+		ext4_warning_inode(inode,
+				   "verity is only allowed on extent-based files");
+		return -EOPNOTSUPP;
+	}
+
+	/*
+	 * ext4 uses the last allocated block to find the verity descriptor, so
+	 * we must remove any other blocks past EOF which might confuse things.
+	 */
+	err = ext4_truncate(inode);
+	if (err)
+		return err;
+
+	handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
+	if (IS_ERR(handle))
+		return PTR_ERR(handle);
+
+	err = ext4_orphan_add(handle, inode);
+	if (err == 0)
+		ext4_set_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
+
+	ext4_journal_stop(handle);
+	return err;
+}
+
+/*
+ * ext4 stores the verity descriptor beginning on the next filesystem block
+ * boundary after the Merkle tree.  Then, the descriptor size is stored in the
+ * last 4 bytes of the last allocated filesystem block --- which is either the
+ * block in which the descriptor ends, or the next block after that if there
+ * weren't at least 4 bytes remaining.
+ *
+ * We can't simply store the descriptor in an xattr because it *must* be
+ * encrypted when ext4 encryption is used, but ext4 encryption doesn't encrypt
+ * xattrs.  Also, if the descriptor includes a large signature blob it may be
+ * too large to store in an xattr without the EA_INODE feature.
+ */
+static int ext4_write_verity_descriptor(struct inode *inode, const void *desc,
+					size_t desc_size, u64 merkle_tree_size)
+{
+	const u64 desc_pos = round_up(ext4_verity_metadata_pos(inode) +
+				      merkle_tree_size, i_blocksize(inode));
+	const u64 desc_end = desc_pos + desc_size;
+	const __le32 desc_size_disk = cpu_to_le32(desc_size);
+	const u64 desc_size_pos = round_up(desc_end + sizeof(desc_size_disk),
+					   i_blocksize(inode)) -
+				  sizeof(desc_size_disk);
+	int err;
+
+	err = pagecache_write(inode, desc, desc_size, desc_pos);
+	if (err)
+		return err;
+
+	return pagecache_write(inode, &desc_size_disk, sizeof(desc_size_disk),
+			       desc_size_pos);
+}
+
+static int ext4_end_enable_verity(struct file *filp, const void *desc,
+				  size_t desc_size, u64 merkle_tree_size)
+{
+	struct inode *inode = file_inode(filp);
+	const int credits = 2; /* superblock and inode for ext4_orphan_del() */
+	handle_t *handle;
+	struct ext4_iloc iloc;
+	int err = 0;
+
+	/*
+	 * If an error already occurred (which fs/verity/ signals by passing
+	 * desc == NULL), then only clean-up is needed.
+	 */
+	if (desc == NULL)
+		goto cleanup;
+
+	/* Append the verity descriptor. */
+	err = ext4_write_verity_descriptor(inode, desc, desc_size,
+					   merkle_tree_size);
+	if (err)
+		goto cleanup;
+
+	/*
+	 * Write all pages (both data and verity metadata).  Note that this must
+	 * happen before clearing EXT4_STATE_VERITY_IN_PROGRESS; otherwise pages
+	 * beyond i_size won't be written properly.  For crash consistency, this
+	 * also must happen before the verity inode flag gets persisted.
+	 */
+	err = filemap_write_and_wait(inode->i_mapping);
+	if (err)
+		goto cleanup;
+
+	/*
+	 * Finally, set the verity inode flag and remove the inode from the
+	 * orphan list (in a single transaction).
+	 */
+
+	handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
+	if (IS_ERR(handle)) {
+		err = PTR_ERR(handle);
+		goto cleanup;
+	}
+
+	err = ext4_orphan_del(handle, inode);
+	if (err)
+		goto stop_and_cleanup;
+
+	err = ext4_reserve_inode_write(handle, inode, &iloc);
+	if (err)
+		goto stop_and_cleanup;
+
+	ext4_set_inode_flag(inode, EXT4_INODE_VERITY);
+	ext4_set_inode_flags(inode, false);
+	err = ext4_mark_iloc_dirty(handle, inode, &iloc);
+	if (err)
+		goto stop_and_cleanup;
+
+	ext4_journal_stop(handle);
+
+	ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
+	return 0;
+
+stop_and_cleanup:
+	ext4_journal_stop(handle);
+cleanup:
+	/*
+	 * Verity failed to be enabled, so clean up by truncating any verity
+	 * metadata that was written beyond i_size (both from cache and from
+	 * disk), removing the inode from the orphan list (if it wasn't done
+	 * already), and clearing EXT4_STATE_VERITY_IN_PROGRESS.
+	 */
+	truncate_inode_pages(inode->i_mapping, inode->i_size);
+	ext4_truncate(inode);
+	ext4_orphan_del(NULL, inode);
+	ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
+	return err;
+}
+
+static int ext4_get_verity_descriptor_location(struct inode *inode,
+					       size_t *desc_size_ret,
+					       u64 *desc_pos_ret)
+{
+	struct ext4_ext_path *path;
+	struct ext4_extent *last_extent;
+	u32 end_lblk;
+	u64 desc_size_pos;
+	__le32 desc_size_disk;
+	u32 desc_size;
+	u64 desc_pos;
+	int err;
+
+	/*
+	 * Descriptor size is in last 4 bytes of last allocated block.
+	 * See ext4_write_verity_descriptor().
+	 */
+
+	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
+		EXT4_ERROR_INODE(inode, "verity file doesn't use extents");
+		return -EFSCORRUPTED;
+	}
+
+	path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+
+	last_extent = path[path->p_depth].p_ext;
+	if (!last_extent) {
+		EXT4_ERROR_INODE(inode, "verity file has no extents");
+		ext4_free_ext_path(path);
+		return -EFSCORRUPTED;
+	}
+
+	end_lblk = le32_to_cpu(last_extent->ee_block) +
+		   ext4_ext_get_actual_len(last_extent);
+	desc_size_pos = (u64)end_lblk << inode->i_blkbits;
+	ext4_free_ext_path(path);
+
+	if (desc_size_pos < sizeof(desc_size_disk))
+		goto bad;
+	desc_size_pos -= sizeof(desc_size_disk);
+
+	err = pagecache_read(inode, &desc_size_disk, sizeof(desc_size_disk),
+			     desc_size_pos);
+	if (err)
+		return err;
+	desc_size = le32_to_cpu(desc_size_disk);
+
+	/*
+	 * The descriptor is stored just before the desc_size_disk, but starting
+	 * on a filesystem block boundary.
+	 */
+
+	if (desc_size > INT_MAX || desc_size > desc_size_pos)
+		goto bad;
+
+	desc_pos = round_down(desc_size_pos - desc_size, i_blocksize(inode));
+	if (desc_pos < ext4_verity_metadata_pos(inode))
+		goto bad;
+
+	*desc_size_ret = desc_size;
+	*desc_pos_ret = desc_pos;
+	return 0;
+
+bad:
+	EXT4_ERROR_INODE(inode, "verity file corrupted; can't find descriptor");
+	return -EFSCORRUPTED;
+}
+
+static int ext4_get_verity_descriptor(struct inode *inode, void *buf,
+				      size_t buf_size)
+{
+	size_t desc_size = 0;
+	u64 desc_pos = 0;
+	int err;
+
+	err = ext4_get_verity_descriptor_location(inode, &desc_size, &desc_pos);
+	if (err)
+		return err;
+
+	if (buf_size) {
+		if (desc_size > buf_size)
+			return -ERANGE;
+		err = pagecache_read(inode, buf, desc_size, desc_pos);
+		if (err)
+			return err;
+	}
+	return desc_size;
+}
+
+static struct page *ext4_read_merkle_tree_page(struct inode *inode,
+					       pgoff_t index,
+					       unsigned long num_ra_pages)
+{
+	struct folio *folio;
+
+	index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;
+
+	folio = __filemap_get_folio(inode->i_mapping, index, FGP_ACCESSED, 0);
+	if (IS_ERR(folio) || !folio_test_uptodate(folio)) {
+		DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
+
+		if (!IS_ERR(folio))
+			folio_put(folio);
+		else if (num_ra_pages > 1)
+			page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
+		folio = read_mapping_folio(inode->i_mapping, index, NULL);
+		if (IS_ERR(folio))
+			return ERR_CAST(folio);
+	}
+	return folio_file_page(folio, index);
+}
+
+static int ext4_write_merkle_tree_block(struct inode *inode, const void *buf,
+					u64 pos, unsigned int size)
+{
+	pos += ext4_verity_metadata_pos(inode);
+
+	return pagecache_write(inode, buf, size, pos);
+}
+
+const struct fsverity_operations ext4_verityops = {
+	.begin_enable_verity	= ext4_begin_enable_verity,
+	.end_enable_verity	= ext4_end_enable_verity,
+	.get_verity_descriptor	= ext4_get_verity_descriptor,
+	.read_merkle_tree_page	= ext4_read_merkle_tree_page,
+	.write_merkle_tree_block = ext4_write_merkle_tree_block,
+};