ext4: add basic fs-verity support
Add most of fs-verity support to ext4. fs-verity is a filesystem
feature that enables transparent integrity protection and authentication
of read-only files. It uses a dm-verity like mechanism at the file
level: a Merkle tree is used to verify any block in the file in
log(filesize) time. It is implemented mainly by helper functions in
fs/verity/. See Documentation/filesystems/fsverity.rst for the full
documentation.
This commit adds all of ext4 fs-verity support except for the actual
data verification, including:
- Adding a filesystem feature flag and an inode flag for fs-verity.
- Implementing the fsverity_operations to support enabling verity on an
inode and reading/writing the verity metadata.
- Updating ->write_begin(), ->write_end(), and ->writepages() to support
writing verity metadata pages.
- Calling the fs-verity hooks for ->open(), ->setattr(), and ->ioctl().
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.
This patch incorporates work by Theodore Ts'o and Chandan Rajendra.
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 420fe3d..6de3d4b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1340,6 +1340,9 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
}
if (ret) {
+ bool extended = (pos + len > inode->i_size) &&
+ !ext4_verity_in_progress(inode);
+
unlock_page(page);
/*
* __block_write_begin may have instantiated a few blocks
@@ -1349,11 +1352,11 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
* Add inode to orphan list in case we crash before
* truncate finishes
*/
- if (pos + len > inode->i_size && ext4_can_truncate(inode))
+ if (extended && ext4_can_truncate(inode))
ext4_orphan_add(handle, inode);
ext4_journal_stop(handle);
- if (pos + len > inode->i_size) {
+ if (extended) {
ext4_truncate_failed_write(inode);
/*
* If truncate failed early the inode might
@@ -1406,6 +1409,7 @@ static int ext4_write_end(struct file *file,
int ret = 0, ret2;
int i_size_changed = 0;
int inline_data = ext4_has_inline_data(inode);
+ bool verity = ext4_verity_in_progress(inode);
trace_ext4_write_end(inode, pos, len, copied);
if (inline_data) {
@@ -1423,12 +1427,16 @@ static int ext4_write_end(struct file *file,
/*
* it's important to update i_size while still holding page lock:
* page writeout could otherwise come in and zero beyond i_size.
+ *
+ * If FS_IOC_ENABLE_VERITY is running on this inode, then Merkle tree
+ * blocks are being written past EOF, so skip the i_size update.
*/
- i_size_changed = ext4_update_inode_size(inode, pos + copied);
+ if (!verity)
+ i_size_changed = ext4_update_inode_size(inode, pos + copied);
unlock_page(page);
put_page(page);
- if (old_size < pos)
+ if (old_size < pos && !verity)
pagecache_isize_extended(inode, old_size, pos);
/*
* Don't mark the inode dirty under page lock. First, it unnecessarily
@@ -1439,7 +1447,7 @@ static int ext4_write_end(struct file *file,
if (i_size_changed || inline_data)
ext4_mark_inode_dirty(handle, inode);
- if (pos + len > inode->i_size && ext4_can_truncate(inode))
+ if (pos + len > inode->i_size && !verity && ext4_can_truncate(inode))
/* if we have allocated more blocks and copied
* less. We will have blocks allocated outside
* inode->i_size. So truncate them
@@ -1450,7 +1458,7 @@ static int ext4_write_end(struct file *file,
if (!ret)
ret = ret2;
- if (pos + len > inode->i_size) {
+ if (pos + len > inode->i_size && !verity) {
ext4_truncate_failed_write(inode);
/*
* If truncate failed early the inode might still be
@@ -1511,6 +1519,7 @@ static int ext4_journalled_write_end(struct file *file,
unsigned from, to;
int size_changed = 0;
int inline_data = ext4_has_inline_data(inode);
+ bool verity = ext4_verity_in_progress(inode);
trace_ext4_journalled_write_end(inode, pos, len, copied);
from = pos & (PAGE_SIZE - 1);
@@ -1540,13 +1549,14 @@ static int ext4_journalled_write_end(struct file *file,
if (!partial)
SetPageUptodate(page);
}
- size_changed = ext4_update_inode_size(inode, pos + copied);
+ if (!verity)
+ size_changed = ext4_update_inode_size(inode, pos + copied);
ext4_set_inode_state(inode, EXT4_STATE_JDATA);
EXT4_I(inode)->i_datasync_tid = handle->h_transaction->t_tid;
unlock_page(page);
put_page(page);
- if (old_size < pos)
+ if (old_size < pos && !verity)
pagecache_isize_extended(inode, old_size, pos);
if (size_changed || inline_data) {
@@ -1555,7 +1565,7 @@ static int ext4_journalled_write_end(struct file *file,
ret = ret2;
}
- if (pos + len > inode->i_size && ext4_can_truncate(inode))
+ if (pos + len > inode->i_size && !verity && ext4_can_truncate(inode))
/* if we have allocated more blocks and copied
* less. We will have blocks allocated outside
* inode->i_size. So truncate them
@@ -1566,7 +1576,7 @@ static int ext4_journalled_write_end(struct file *file,
ret2 = ext4_journal_stop(handle);
if (!ret)
ret = ret2;
- if (pos + len > inode->i_size) {
+ if (pos + len > inode->i_size && !verity) {
ext4_truncate_failed_write(inode);
/*
* If truncate failed early the inode might still be
@@ -2162,7 +2172,8 @@ static int ext4_writepage(struct page *page,
trace_ext4_writepage(page);
size = i_size_read(inode);
- if (page->index == size >> PAGE_SHIFT)
+ if (page->index == size >> PAGE_SHIFT &&
+ !ext4_verity_in_progress(inode))
len = size & ~PAGE_MASK;
else
len = PAGE_SIZE;
@@ -2246,7 +2257,8 @@ static int mpage_submit_page(struct mpage_da_data *mpd, struct page *page)
* after page tables are updated.
*/
size = i_size_read(mpd->inode);
- if (page->index == size >> PAGE_SHIFT)
+ if (page->index == size >> PAGE_SHIFT &&
+ !ext4_verity_in_progress(mpd->inode))
len = size & ~PAGE_MASK;
else
len = PAGE_SIZE;
@@ -2345,6 +2357,9 @@ static int mpage_process_page_bufs(struct mpage_da_data *mpd,
ext4_lblk_t blocks = (i_size_read(inode) + i_blocksize(inode) - 1)
>> inode->i_blkbits;
+ if (ext4_verity_in_progress(inode))
+ blocks = EXT_MAX_BLOCKS;
+
do {
BUG_ON(buffer_locked(bh));
@@ -3061,8 +3076,8 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
index = pos >> PAGE_SHIFT;
- if (ext4_nonda_switch(inode->i_sb) ||
- S_ISLNK(inode->i_mode)) {
+ if (ext4_nonda_switch(inode->i_sb) || S_ISLNK(inode->i_mode) ||
+ ext4_verity_in_progress(inode)) {
*fsdata = (void *)FALL_BACK_TO_NONDELALLOC;
return ext4_write_begin(file, mapping, pos,
len, flags, pagep, fsdata);
@@ -4739,6 +4754,8 @@ static bool ext4_should_use_dax(struct inode *inode)
return false;
if (ext4_test_inode_flag(inode, EXT4_INODE_ENCRYPT))
return false;
+ if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY))
+ return false;
return true;
}
@@ -4763,9 +4780,11 @@ void ext4_set_inode_flags(struct inode *inode)
new_fl |= S_ENCRYPTED;
if (flags & EXT4_CASEFOLD_FL)
new_fl |= S_CASEFOLD;
+ if (flags & EXT4_VERITY_FL)
+ new_fl |= S_VERITY;
inode_set_flags(inode, new_fl,
S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX|
- S_ENCRYPTED|S_CASEFOLD);
+ S_ENCRYPTED|S_CASEFOLD|S_VERITY);
}
static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
@@ -5555,6 +5574,10 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
if (error)
return error;
+ error = fsverity_prepare_setattr(dentry, attr);
+ if (error)
+ return error;
+
if (is_quota_modification(inode, attr)) {
error = dquot_initialize(inode);
if (error)
