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Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , David Hildenbrand , Kees Cook , Jeff Xu , Andrey Vagin , Alexander Mikhalitsyn , Paul Moore , James Morris , "Serge E. Hallyn" , Shuah Khan , Jonathan Corbet , linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 1/3] mseal sysmap: Add mseal_system_mappings= boot parameter Message-ID: References: <5bd3c89d733ad22224f296dfa8900769de937de0.1793094611.git.chris@chrisdown.name> <18e2972cb8520c2e.3137322e32382e342e3434.279dd1.0000sendgmr@google.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: B482C40004 X-Stat-Signature: wr6f1zzy5a78zz1tsjdg3m1zn9caeo3r X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793180959-425779 X-HE-Meta: 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 5CNNAtQO tsAdbPeJ/fdq3/Lw77AEVdVQ+ZE4Pdm0nkpU6zlx2mmxx0b5NVXbHHRT9WVlKyu3/Tox7bwduFImaVK1AElppabDGSZ7/Gb1Pwqg6QVV+JGO0HRM4rYM7FWQsFCbZnsHcsfZTHh7aeOyHY30zuZFzZLHhhBiO7Ei7EnO8/dyDSCN5W4zddvBHgFhHJ4ozgw+oLFT3yry0DefgoA5nSKHdCOrwQd6fvak3sFohfPIwOrDeSskvbE2vbwgzpwCyY6MDC1jG1SVndwt3x3kjBxtQoUEw2cWahTz37BLAjLV1ywM78wE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, Oct 28, 2026 at 01:52:18PM +0800, Chris Down wrote: > Hi Jeff, > > Thanks for the review! > > Jeff Xu writes: > > Could we please keep the test coverage for the unsealed [vdso] case and > > avoid unconditionally skipping whenever [vdso] is unsealed? > > > > There are two regressions I'd love for us to still be able to catch: > > > > 1. Kernel or config regressions when sealing is expected to be on: > > Yeah agreed. With the cleanup it matters even more I think because when > sealing is set in one place the most likely regression is probably one that > unseals everything at once. > > > 2. Regressions in the new `no_mseal_sys_mappings` boot parameter itself: > > In v2 I can check /proc/cmdline for no_mseal_sys_mappings to do that. > > Lorenzo, I think that also may inform your question about whether checking > for the disabled case is redundant, right? > > > When booted with `no_mseal_sys_mappings` (or when unsealed), running > > the assertions in Patch 3 (verifying system mappings have no `sl` flag > > and that `munmap()` / `mremap()` -- and ideally `mprotect(PROT_READ | > > PROT_WRITE)` -- on [vdso] succeed) directly verifies that the boot > > parameter works and doesn't regress. > > Sounds good. > > > or keep strict failure as an option (e.g. `./sysmap_is_sealed` fails if > > unsealed without the boot param, while `run_vmtests.sh` passes a flag > > like `--allow-disabled` when `CONFIG_MSEAL_SYSTEM_MAPPINGS` may not be > > enabled), so CI environments that expect sealing still catch a broken > > seal. > > I like this and I think we can do it without adding some of the complexity > that Lorenzo was not so happy about: > > - Have check_sealed skip as usual when [vdso] isn't sealed and param is not set > - A new test, say expect_sealed, fails in the same case I'm confused about this one - we want to skip altogether if the feature isn't enabled, right? > - run_vmtests runs with -T expect_sealed when CONFIG_MSEAL_SYSTEM_MAPPINGS=y run_vmtests I will have to best-guess it, e.g. if /proc/config.gz is present check it, I suppose? > > That should be pretty minimal. Lorenzo, Jeff, how does that sound? Sounds reasonable! I am a bit leery though of requiring a CI to enable the option when it is known to break things, however, as CI's might rely on some of the software this impacts. -- Cheers, Lorenzo