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authorEric Biggers <ebiggers@google.com>2019-07-22 09:26:24 -0700
committerEric Biggers <ebiggers@google.com>2019-08-12 19:33:50 -0700
commitc93d8f88580921c84d2213161ef3c22560511b84 (patch)
treea113a5c4cbb04d656ebf22f10193745602d923c3 /fs/ext4/sysfs.c
parent432434c9f8e18cb4cf0fe05bc3eeceada0e10dc6 (diff)
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>
Diffstat (limited to 'fs/ext4/sysfs.c')
-rw-r--r--fs/ext4/sysfs.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
index b3cd7655a6ff..eb1efad0e20a 100644
--- a/fs/ext4/sysfs.c
+++ b/fs/ext4/sysfs.c
@@ -242,6 +242,9 @@ EXT4_ATTR_FEATURE(encryption);
#ifdef CONFIG_UNICODE
EXT4_ATTR_FEATURE(casefold);
#endif
+#ifdef CONFIG_FS_VERITY
+EXT4_ATTR_FEATURE(verity);
+#endif
EXT4_ATTR_FEATURE(metadata_csum_seed);
static struct attribute *ext4_feat_attrs[] = {
@@ -254,6 +257,9 @@ static struct attribute *ext4_feat_attrs[] = {
#ifdef CONFIG_UNICODE
ATTR_LIST(casefold),
#endif
+#ifdef CONFIG_FS_VERITY
+ ATTR_LIST(verity),
+#endif
ATTR_LIST(metadata_csum_seed),
NULL,
};