mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
403 lines
11 KiB
403 lines
11 KiB
// 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; |
|
void *addr; |
|
|
|
page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT, |
|
NULL); |
|
if (IS_ERR(page)) |
|
return PTR_ERR(page); |
|
|
|
addr = kmap_atomic(page); |
|
memcpy(buf, addr + offset_in_page(pos), n); |
|
kunmap_atomic(addr); |
|
|
|
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; |
|
void *addr; |
|
int res; |
|
|
|
res = pagecache_write_begin(NULL, inode->i_mapping, pos, n, 0, |
|
&page, &fsdata); |
|
if (res) |
|
return res; |
|
|
|
addr = kmap_atomic(page); |
|
memcpy(addr + offset_in_page(pos), buf, n); |
|
kunmap_atomic(addr); |
|
|
|
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, 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, |
|
};
|
|
|