ext4: refuse encryption when block size > page size

Hi,

encryption is not supported when a filesystem's block size is larger than the page size. Although the kernel refuses to mount such a filesystem if the "encrypt" feature is already set, it is possible to enable it on a mounted filesystem with e.g. tune2fs.

# mkfs.ext4 -b 16384 /dev/vdb
# mount /dev/vdb /mnt/
# tune2fs -O encrypt /dev/vdb
# mkdir /mnt/foo
# fscrypt setup /mnt
# fscrypt encrypt /mnt/foo/
# head -c 20M /dev/urandom > /mnt/foo/data
# sync
[  116.014221] EXT4-fs warning (device vdb): ext4_end_bio:360: I/O error 19 writing to inode 19 starting block 130040)
[  116.014235] EXT4-fs (vdb): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -5)
[  116.014241] Buffer I/O error on device vdb, logical block 130040
[...]
[  116.014264] Buffer I/O error on device vdb, logical block 130049
[  116.015505] EXT4-fs warning (device vdb): ext4_end_bio:360: I/O error 19 writing to inode 19 starting block 66552)
[  116.015520] EXT4-fs (vdb): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -5)
[  116.016451] EXT4-fs warning (device vdb): ext4_end_bio:360: I/O error 19 writing to inode 19 starting block 65784)
[  116.016459] EXT4-fs (vdb): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -5)

This affects all kernels starting from v6.19 up to v7.3-rc4.

Note that this still allows encrypted inodes even when the 'encrypt' feature is missing as long as block size <= page size. With v1 encryption policies they can be used normally.

There's an additional bug that only affects kernels between v6.19 and v7.2 (but not v7.3), which will be dealt with separately.

Regards,

Berto

Alberto Garcia (2):
ext4: refuse encryption when block size > page size
ext4: reject encrypted inodes when block size > page size

 fs/ext4/crypto.c | 9 +++++++++
 fs/ext4/inode.c  | 6 ++++++
 2 files changed, 15 insertions(+)

2.47.3