From: Eric Biggers <ebiggers@xxxxxxxxxx>
In order to maximize the chance that the verity tests can actually be
run, FSV_BLOCK_SIZE (the default Merkle tree size for the verity tests)
needs to be min(fs_block_size, page_size), not simply page_size. The
only reason that page_size was okay before was because the kernel only
supported merkle_tree_block_size == fs_block_size == page_size anyway.
But that is changing.
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
common/verity | 32 +++++++++++++++++++++++++++-----
1 file changed, 27 insertions(+), 5 deletions(-)
diff --git a/common/verity b/common/verity
index 1a53a7ea..a94ebf8e 100644
--- a/common/verity
+++ b/common/verity
@@ -13,6 +13,11 @@ if [ "$FSTYP" == "btrfs" ]; then
fi
fi
+# Require fs-verity support on the scratch filesystem.
+#
+# FSV_BLOCK_SIZE will be set to a Merkle tree block size that is supported by
+# the filesystem. Other sizes may be supported too, but FSV_BLOCK_SIZE is the
+# only size that is guaranteed to work without any additional checks.
_require_scratch_verity()
{
_require_scratch
@@ -27,7 +32,7 @@ _require_scratch_verity()
# Try to mount the filesystem. If this fails then either the kernel
# isn't aware of fs-verity, or the mkfs options were not compatible with
- # verity (e.g. ext4 with block size != PAGE_SIZE).
+ # verity (e.g. ext4 with block size != PAGE_SIZE on old kernels).
if ! _try_scratch_mount &>>$seqres.full; then
_notrun "kernel is unaware of $FSTYP verity feature," \
"or mkfs options are not compatible with verity"
@@ -39,6 +44,27 @@ _require_scratch_verity()
_notrun "kernel $FSTYP isn't configured with verity support"
fi
+ # Select a default Merkle tree block size for when tests don't
+ # explicitly specify one.
+ #
+ # For consistency reasons, all 'fsverity' subcommands, including
+ # 'fsverity enable', default to 4K Merkle tree blocks. That's generally
+ # not ideal for tests, since it's possible that the filesystem doesn't
+ # support 4K blocks but does support another size. Specifically, the
+ # kernel originally supported only merkle_tree_block_size ==
+ # fs_block_size == page_size, and later it was updated to support
+ # merkle_tree_block_size <= min(fs_block_size, page_size).
+ #
+ # Therefore, we default to merkle_tree_block_size == min(fs_block_size,
+ # page_size). That maximizes the chance of verity actually working.
+ local fs_block_size=$(_get_block_size $SCRATCH_MNT)
+ local page_size=$(get_page_size)
+ if (( fs_block_size <= page_size )); then
+ FSV_BLOCK_SIZE=$fs_block_size
+ else
+ FSV_BLOCK_SIZE=$page_size
+ fi
+
# The filesystem may have fs-verity enabled but not actually usable by
# default. E.g., ext4 only supports verity on extent-based files, so it
# doesn't work on ext3-style filesystems. So, try actually using it.
@@ -47,10 +73,6 @@ _require_scratch_verity()
fi
_scratch_unmount
-
- # Merkle tree block size. Currently all filesystems only support
- # PAGE_SIZE for this. This is also the default for 'fsverity enable'.
- FSV_BLOCK_SIZE=$(get_page_size)
}
# Check for CONFIG_FS_VERITY_BUILTIN_SIGNATURES=y, as well as the userspace
--
2.39.0
|