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1da86618bd
Convert all callers from working on a page to working on one page of a folio (support for working on an entire folio can come later). Removes a lot of folio->page->folio conversions. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
398 lines
11 KiB
C
398 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* fs/ext4/verity.c: fs-verity support for ext4
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*
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* Copyright 2019 Google LLC
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*/
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/*
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* Implementation of fsverity_operations for ext4.
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*
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* ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past
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* the end of the file, starting at the first 64K boundary beyond i_size. This
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* approach works because (a) verity files are readonly, and (b) pages fully
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* beyond i_size aren't visible to userspace but can be read/written internally
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* by ext4 with only some relatively small changes to ext4. This approach
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* avoids having to depend on the EA_INODE feature and on rearchitecturing
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* ext4's xattr support to support paging multi-gigabyte xattrs into memory, and
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* to support encrypting xattrs. Note that the verity metadata *must* be
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* encrypted when the file is, since it contains hashes of the plaintext data.
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*
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* Using a 64K boundary rather than a 4K one keeps things ready for
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* architectures with 64K pages, and it doesn't necessarily waste space on-disk
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* since there can be a hole between i_size and the start of the Merkle tree.
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*/
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#include <linux/quotaops.h>
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#include "ext4.h"
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#include "ext4_extents.h"
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#include "ext4_jbd2.h"
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static inline loff_t ext4_verity_metadata_pos(const struct inode *inode)
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{
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return round_up(inode->i_size, 65536);
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}
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/*
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* Read some verity metadata from the inode. __vfs_read() can't be used because
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* we need to read beyond i_size.
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*/
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static int pagecache_read(struct inode *inode, void *buf, size_t count,
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loff_t pos)
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{
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while (count) {
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struct folio *folio;
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size_t n;
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folio = read_mapping_folio(inode->i_mapping, pos >> PAGE_SHIFT,
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NULL);
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if (IS_ERR(folio))
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return PTR_ERR(folio);
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n = memcpy_from_file_folio(buf, folio, pos, count);
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folio_put(folio);
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buf += n;
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pos += n;
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count -= n;
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}
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return 0;
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}
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/*
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* Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
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* kernel_write() can't be used because the file descriptor is readonly.
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*/
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static int pagecache_write(struct inode *inode, const void *buf, size_t count,
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loff_t pos)
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{
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struct address_space *mapping = inode->i_mapping;
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const struct address_space_operations *aops = mapping->a_ops;
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if (pos + count > inode->i_sb->s_maxbytes)
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return -EFBIG;
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while (count) {
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size_t n = min_t(size_t, count,
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PAGE_SIZE - offset_in_page(pos));
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struct folio *folio;
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void *fsdata = NULL;
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int res;
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res = aops->write_begin(NULL, mapping, pos, n, &folio, &fsdata);
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if (res)
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return res;
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memcpy_to_folio(folio, offset_in_folio(folio, pos), buf, n);
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res = aops->write_end(NULL, mapping, pos, n, n, folio, fsdata);
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if (res < 0)
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return res;
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if (res != n)
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return -EIO;
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buf += n;
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pos += n;
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count -= n;
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}
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return 0;
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}
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static int ext4_begin_enable_verity(struct file *filp)
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{
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struct inode *inode = file_inode(filp);
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const int credits = 2; /* superblock and inode for ext4_orphan_add() */
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handle_t *handle;
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int err;
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if (IS_DAX(inode) || ext4_test_inode_flag(inode, EXT4_INODE_DAX))
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return -EINVAL;
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if (ext4_verity_in_progress(inode))
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return -EBUSY;
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/*
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* Since the file was opened readonly, we have to initialize the jbd
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* inode and quotas here and not rely on ->open() doing it. This must
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* be done before evicting the inline data.
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*/
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err = ext4_inode_attach_jinode(inode);
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if (err)
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return err;
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err = dquot_initialize(inode);
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if (err)
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return err;
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err = ext4_convert_inline_data(inode);
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if (err)
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return err;
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if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
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ext4_warning_inode(inode,
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"verity is only allowed on extent-based files");
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return -EOPNOTSUPP;
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}
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/*
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* ext4 uses the last allocated block to find the verity descriptor, so
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* we must remove any other blocks past EOF which might confuse things.
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*/
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err = ext4_truncate(inode);
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if (err)
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return err;
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handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
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if (IS_ERR(handle))
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return PTR_ERR(handle);
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err = ext4_orphan_add(handle, inode);
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if (err == 0)
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ext4_set_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
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ext4_journal_stop(handle);
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return err;
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}
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/*
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* ext4 stores the verity descriptor beginning on the next filesystem block
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* boundary after the Merkle tree. Then, the descriptor size is stored in the
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* last 4 bytes of the last allocated filesystem block --- which is either the
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* block in which the descriptor ends, or the next block after that if there
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* weren't at least 4 bytes remaining.
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*
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* We can't simply store the descriptor in an xattr because it *must* be
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* encrypted when ext4 encryption is used, but ext4 encryption doesn't encrypt
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* xattrs. Also, if the descriptor includes a large signature blob it may be
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* too large to store in an xattr without the EA_INODE feature.
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*/
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static int ext4_write_verity_descriptor(struct inode *inode, const void *desc,
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size_t desc_size, u64 merkle_tree_size)
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{
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const u64 desc_pos = round_up(ext4_verity_metadata_pos(inode) +
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merkle_tree_size, i_blocksize(inode));
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const u64 desc_end = desc_pos + desc_size;
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const __le32 desc_size_disk = cpu_to_le32(desc_size);
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const u64 desc_size_pos = round_up(desc_end + sizeof(desc_size_disk),
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i_blocksize(inode)) -
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sizeof(desc_size_disk);
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int err;
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err = pagecache_write(inode, desc, desc_size, desc_pos);
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if (err)
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return err;
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return pagecache_write(inode, &desc_size_disk, sizeof(desc_size_disk),
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desc_size_pos);
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}
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static int ext4_end_enable_verity(struct file *filp, const void *desc,
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size_t desc_size, u64 merkle_tree_size)
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{
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struct inode *inode = file_inode(filp);
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const int credits = 2; /* superblock and inode for ext4_orphan_del() */
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handle_t *handle;
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struct ext4_iloc iloc;
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int err = 0;
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/*
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* If an error already occurred (which fs/verity/ signals by passing
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* desc == NULL), then only clean-up is needed.
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*/
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if (desc == NULL)
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goto cleanup;
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/* Append the verity descriptor. */
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err = ext4_write_verity_descriptor(inode, desc, desc_size,
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merkle_tree_size);
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if (err)
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goto cleanup;
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/*
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* Write all pages (both data and verity metadata). Note that this must
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* happen before clearing EXT4_STATE_VERITY_IN_PROGRESS; otherwise pages
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* beyond i_size won't be written properly. For crash consistency, this
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* also must happen before the verity inode flag gets persisted.
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*/
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err = filemap_write_and_wait(inode->i_mapping);
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if (err)
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goto cleanup;
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/*
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* Finally, set the verity inode flag and remove the inode from the
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* orphan list (in a single transaction).
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*/
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handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
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if (IS_ERR(handle)) {
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err = PTR_ERR(handle);
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goto cleanup;
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}
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err = ext4_orphan_del(handle, inode);
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if (err)
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goto stop_and_cleanup;
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err = ext4_reserve_inode_write(handle, inode, &iloc);
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if (err)
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goto stop_and_cleanup;
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ext4_set_inode_flag(inode, EXT4_INODE_VERITY);
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ext4_set_inode_flags(inode, false);
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err = ext4_mark_iloc_dirty(handle, inode, &iloc);
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if (err)
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goto stop_and_cleanup;
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ext4_journal_stop(handle);
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ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
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return 0;
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stop_and_cleanup:
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ext4_journal_stop(handle);
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cleanup:
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/*
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* Verity failed to be enabled, so clean up by truncating any verity
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* metadata that was written beyond i_size (both from cache and from
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* disk), removing the inode from the orphan list (if it wasn't done
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* already), and clearing EXT4_STATE_VERITY_IN_PROGRESS.
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*/
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truncate_inode_pages(inode->i_mapping, inode->i_size);
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ext4_truncate(inode);
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ext4_orphan_del(NULL, inode);
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ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
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return err;
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}
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static int ext4_get_verity_descriptor_location(struct inode *inode,
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size_t *desc_size_ret,
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u64 *desc_pos_ret)
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{
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struct ext4_ext_path *path;
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struct ext4_extent *last_extent;
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u32 end_lblk;
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u64 desc_size_pos;
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__le32 desc_size_disk;
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u32 desc_size;
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u64 desc_pos;
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int err;
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/*
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* Descriptor size is in last 4 bytes of last allocated block.
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* See ext4_write_verity_descriptor().
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*/
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if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
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EXT4_ERROR_INODE(inode, "verity file doesn't use extents");
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return -EFSCORRUPTED;
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}
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path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
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if (IS_ERR(path))
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return PTR_ERR(path);
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last_extent = path[path->p_depth].p_ext;
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if (!last_extent) {
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EXT4_ERROR_INODE(inode, "verity file has no extents");
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ext4_free_ext_path(path);
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return -EFSCORRUPTED;
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}
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end_lblk = le32_to_cpu(last_extent->ee_block) +
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ext4_ext_get_actual_len(last_extent);
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desc_size_pos = (u64)end_lblk << inode->i_blkbits;
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ext4_free_ext_path(path);
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if (desc_size_pos < sizeof(desc_size_disk))
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goto bad;
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desc_size_pos -= sizeof(desc_size_disk);
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err = pagecache_read(inode, &desc_size_disk, sizeof(desc_size_disk),
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desc_size_pos);
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if (err)
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return err;
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desc_size = le32_to_cpu(desc_size_disk);
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/*
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* The descriptor is stored just before the desc_size_disk, but starting
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* on a filesystem block boundary.
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*/
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if (desc_size > INT_MAX || desc_size > desc_size_pos)
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goto bad;
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desc_pos = round_down(desc_size_pos - desc_size, i_blocksize(inode));
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if (desc_pos < ext4_verity_metadata_pos(inode))
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goto bad;
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*desc_size_ret = desc_size;
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*desc_pos_ret = desc_pos;
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return 0;
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bad:
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EXT4_ERROR_INODE(inode, "verity file corrupted; can't find descriptor");
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return -EFSCORRUPTED;
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}
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static int ext4_get_verity_descriptor(struct inode *inode, void *buf,
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size_t buf_size)
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{
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size_t desc_size = 0;
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u64 desc_pos = 0;
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int err;
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err = ext4_get_verity_descriptor_location(inode, &desc_size, &desc_pos);
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if (err)
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return err;
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if (buf_size) {
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if (desc_size > buf_size)
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return -ERANGE;
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err = pagecache_read(inode, buf, desc_size, desc_pos);
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if (err)
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return err;
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}
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return desc_size;
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}
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static struct page *ext4_read_merkle_tree_page(struct inode *inode,
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pgoff_t index,
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unsigned long num_ra_pages)
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{
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struct folio *folio;
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index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;
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folio = __filemap_get_folio(inode->i_mapping, index, FGP_ACCESSED, 0);
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if (IS_ERR(folio) || !folio_test_uptodate(folio)) {
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DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
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if (!IS_ERR(folio))
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folio_put(folio);
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else if (num_ra_pages > 1)
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page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
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folio = read_mapping_folio(inode->i_mapping, index, NULL);
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if (IS_ERR(folio))
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return ERR_CAST(folio);
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}
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return folio_file_page(folio, index);
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}
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static int ext4_write_merkle_tree_block(struct inode *inode, const void *buf,
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u64 pos, unsigned int size)
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{
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pos += ext4_verity_metadata_pos(inode);
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return pagecache_write(inode, buf, size, pos);
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}
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const struct fsverity_operations ext4_verityops = {
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.begin_enable_verity = ext4_begin_enable_verity,
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.end_enable_verity = ext4_end_enable_verity,
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.get_verity_descriptor = ext4_get_verity_descriptor,
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.read_merkle_tree_page = ext4_read_merkle_tree_page,
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.write_merkle_tree_block = ext4_write_merkle_tree_block,
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};
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