erofs-freebsd-out-tree/tests/TC112-invalid-superblock.md

Test Case: Invalid Superblock Magic

Test ID: TC112-invalid-superblock Category: Error Handling Priority: Critical

Objective

Verify rejection of an invalid EROFS magic at the real field while provider length and all suffix bytes covered by repo22's production checksum verifier remain unchanged.

Fixture Qualification

work=$(mktemp -d /tmp/repo22-tc112.XXXXXX)
tests/prepare_error_fixtures.sh "$work/fixtures"
od -An -tx4 -j 1024 -N 4 "$work/fixtures/bad-magic.erofs"
python3 tests/erofs_fixture.py inspect "$work/fixtures/bad-magic.erofs"
grep '^bad-magic ' "$work/fixtures/fixture-evidence.txt"
wc -c "$work/fixtures/valid-plain.erofs" \
  "$work/fixtures/bad-magic.erofs"
sha256 -q "$work/fixtures/bad-magic.erofs"

The mutator asserts magic 0xe0f5e1e2 at byte 1024 and replaces it with 0x21444142. It intentionally leaves the stored checksum unchanged. The canonical checksum over the changed magic is invalid, but the production fixed-magic suffix calculation over [1032,4096) remains valid because no suffix byte changed. Magic validation occurs first.

FreeBSD Procedure

mkdir "$work/mnt"
unit=$(mdconfig -a -t vnode -f "$work/fixtures/bad-magic.erofs")
set +e
mount -t erofs -o ro "/dev/$unit" "$work/mnt" \
  >"$work/mount.out" 2>"$work/mount.err"
status=$?
set -e
test "$status" -ne 0
set +e
truss -o "$work/mount.truss" mount -t erofs -o ro "/dev/$unit" \
  "$work/mnt" >/dev/null 2>&1
set -e
grep -E 'nmount.*ERR#22' "$work/mount.truss"
! mount -p | awk -v path="$work/mnt" '$2 == path { found=1 }
  END { exit found ? 0 : 1 }'
mdconfig -d -u "${unit#md}"

Expected Results

Mount returns errno 22 (EINVAL) before root vnode creation. No panic, mount, or md consumer remains.