linux/fs/ext4/verity.c
Linus Torvalds 9f67672a81 New features for ext4 this cycle include support for encrypted
casefold, ensure that deleted file names are cleared in directory
 blocks by zeroing directory entries when they are unlinked or moved as
 part of a hash tree node split.  We also improve the block allocator's
 performance on a freshly mounted file system by prefetching block
 bitmaps.
 
 There are also the usual cleanups and bug fixes, including fixing a
 page cache invalidation race when there is mixed buffered and direct
 I/O and the block size is less than page size, and allow the dax flag
 to be set and cleared on inline directories.
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Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 updates from Ted Ts'o:
 "New features for ext4 this cycle include support for encrypted
  casefold, ensure that deleted file names are cleared in directory
  blocks by zeroing directory entries when they are unlinked or moved as
  part of a hash tree node split. We also improve the block allocator's
  performance on a freshly mounted file system by prefetching block
  bitmaps.

  There are also the usual cleanups and bug fixes, including fixing a
  page cache invalidation race when there is mixed buffered and direct
  I/O and the block size is less than page size, and allow the dax flag
  to be set and cleared on inline directories"

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (32 commits)
  ext4: wipe ext4_dir_entry2 upon file deletion
  ext4: Fix occasional generic/418 failure
  fs: fix reporting supported extra file attributes for statx()
  ext4: allow the dax flag to be set and cleared on inline directories
  ext4: fix debug format string warning
  ext4: fix trailing whitespace
  ext4: fix various seppling typos
  ext4: fix error return code in ext4_fc_perform_commit()
  ext4: annotate data race in jbd2_journal_dirty_metadata()
  ext4: annotate data race in start_this_handle()
  ext4: fix ext4_error_err save negative errno into superblock
  ext4: fix error code in ext4_commit_super
  ext4: always panic when errors=panic is specified
  ext4: delete redundant uptodate check for buffer
  ext4: do not set SB_ACTIVE in ext4_orphan_cleanup()
  ext4: make prefetch_block_bitmaps default
  ext4: add proc files to monitor new structures
  ext4: improve cr 0 / cr 1 group scanning
  ext4: add MB_NUM_ORDERS macro
  ext4: add mballoc stats proc file
  ...
2021-04-30 15:35:30 -07:00

398 lines
11 KiB
C

// 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) {
size_t n = min_t(size_t, count,
PAGE_SIZE - offset_in_page(pos));
struct page *page;
page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
NULL);
if (IS_ERR(page))
return PTR_ERR(page);
memcpy_from_page(buf, page, offset_in_page(pos), n);
put_page(page);
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)
{
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;
int res;
res = pagecache_write_begin(NULL, inode->i_mapping, pos, n, 0,
&page, &fsdata);
if (res)
return res;
memcpy_to_page(page, offset_in_page(pos), buf, n);
res = pagecache_write_end(NULL, inode->i_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_ext_drop_refs(path);
kfree(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_ext_drop_refs(path);
kfree(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)
{
DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
struct page *page;
index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;
page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED);
if (!page || !PageUptodate(page)) {
if (page)
put_page(page);
else if (num_ra_pages > 1)
page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
page = read_mapping_page(inode->i_mapping, index, NULL);
}
return page;
}
static int ext4_write_merkle_tree_block(struct inode *inode, const void *buf,
u64 index, int log_blocksize)
{
loff_t pos = ext4_verity_metadata_pos(inode) + (index << log_blocksize);
return pagecache_write(inode, buf, 1 << log_blocksize, 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,
};