A verified FIT is authentic but not necessarily current: replacing the
next-stage image with an older, still correctly signed image reintroduces
vulnerabilities fixed in newer firmware. This series adds opt-in software
rollback protection to the SPL verified FIT flow.
Patch 1 adds CONFIG_SPL_MINIMUM_FIT_VERSION: after signature verification
succeeds, SPL compares the configuration's "version" property (covered by
the signature; missing counts as 0) against the minimum and refuses to
boot a lower version. The default of 0 disables the check, so existing
boards are unaffected unless they opt in.
Patch 2 documents the mechanism, including its trust-root boundary: the
minimum version lives in the SPL binary itself, so this is a software
trust root only.
Related work: "Add anti-rollback validation feature" by Sean Edmond
(2023, Patchwork series 372657, currently changes-requested) addresses
anti-rollback at the OS/boot-flow level; this series instead targets the
SPL FIT configuration-verification step and is complementary to
monotonic-counter approaches (RPMB/TEE-based).
Validation: the same mechanism was validated on real StarFive
VisionFive2 (JH7110) hardware against a vendor 2026.07-based tree:
signed version=2 FITs pass (cold boot x3), a correctly signed version=1
image is rejected with a dedicated message independently of hash
verification, and recovery was re-verified. This series was replayed on
v2026.07 and builds for starfive_visionfive2_defconfig with
CONFIG_SPL_FIT_SIGNATURE=y / CONFIG_SPL_MINIMUM_FIT_VERSION=2; the SPL
binary contains both the hash-verification and rollback-check strings.
eli (2):
spl: fit: add software rollback protection for verified FIT
configurations
doc: spl: describe SPL FIT anti-rollback usage
boot/Kconfig | 11 +++++++++++
common/spl/spl_fit.c | 24 ++++++++++++++++++++++++
doc/develop/spl.rst | 43 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 78 insertions(+)
--
2.53.0
