** Description changed: [Impact] - snap-confine from snapd uses libseccomp to filter various system calls - for confinement. The current version in eoan/bionic/xenial (2.4.1) is - missing knowledge of various system calls for various architectures. As - such this causes strange issues like python snaps segfaulting + The combination of snap-confine and snap-seccomp from snapd uses + libseccomp to filter various system calls for confinement. The current + version in eoan/bionic/xenial (2.4.1) is missing knowledge of various + system calls for various architectures. As such this causes strange + issues like python snaps segfaulting (https://github.com/snapcore/core20/issues/48) or the inadvertent denial of system calls which should be permitted by the base policy (https://forum.snapcraft.io/t/getrlimit-blocked-by-seccomp-on-focal- arm64/17237). libseccomp in groovy is using the latest upstream base release (2.4.3) plus it includes a patch to add some missing aarch64 system calls (https://bugs.launchpad.net/ubuntu/+source/libseccomp/+bug/1877633). SRUing this version back to older stable releases allows libseccomp to operate correctly on all supported architectures. + + + Included as part of this SRU are test-suite reliability improvements - currently the xenial libseccomp package overrides test-suite failures at build time to ignore failures. This masks the fact that on ppc64el and s390x there are currently test suite failures at build time for xenial - these failures occur since libseccomp now includes knowledge of system calls for these architectures but which the linux-libc-dev package for xenial does not actually define (since this is based of the 4.4 kernel in xenial whereas libseccomp 2.4.1 in xenial has knowledge of all system calls up to 5.4). + + In this SRU I have instead fixed the test suite failures for xenial by + including a local (test-suite specific) set of architecture specific + kernel headers from the linux-libc-dev in focal for all releases. These + are just the headers which define the system call numbers for each + architecture *and* these are added to tests/include/$ARCH in the source + package (and tests/Makefile.am is then updated to include these new + headers only). As such this ensures the actual build of libseccomp or + any of the tools does not reference these headers. This allows the test + suite in libseccomp to then be aware of theses system calls and so all + unit tests for all architectures now pass. + + In any future updates for libseccomp to add new system calls, we can + then similarly update these local headers to ensure the unit tests + continue to work as expected. [Test Case] libseccomp includes a significant unit test suite that is run during the build and as part of autopkgtests. To verify the new aarch64 system calls are resolved as expected the scmp_sys_resolver command can be used as well: $ scmp_sys_resolver -a aarch64 getrlimit 163 (whereas in the current version in focal this returns -10180 as libseccomp was not aware of this system-call at compile-time). As part of this SRU, the test suite in libseccomp has been patched to include a local copy of the architecture-specific kernel headers from the 5.4 kernel in focal *for all releases*, so that all system calls which are defined for the 5.4 kernel are known about *for the libseccomp test suite*. This allows all unit tests to pass on older releases as well and defaults the build to fail on unit test failures (whereas currently in xenial this has been overridden to ignore failures). [Regression Potential] This has a low regression potential due to significant testing with many packages that depend on libseccomp (lxc, qemu, snapd, apt, man etc) and - none have shown any regression using this new version. + none have shown any regression using this new version. The re-enablement + of build failure on test failure at build time also ensures that we can + reliably detect FTBFS issues in the future. + + No symbols have been removed (or added) with this update in version so + there is no chance of regression due to ABI change etc. In the past, the + security team has performed more significant version upgrades for + libseccomp (2.2, 2.3, 2.4) -> 2.4.1 without major incident. In the case + of *this* SRU, we are only doing a micro-version upgrade from 2.4.1 to + 2.4.3 so this carries even less change of regressions. Any possible regressions may include applications now seeing correct system call resolution whereas previously this would have failed, and so perhaps previous failures (which were erroneous) will now be permitted. However, this was always permitted previously by the policy anyway but just denied due to this bug so it is not a true regression as such. + + + I have prepared these updates in the ubuntu-security-proposed PPA - could the SRU team could please review these in lieu of attached debdiffs?
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1876055 Title: SRU: Backport 2.4.3-1ubuntu2 from groovy to focal/eoan/bionic/xenial for newer syscalls for core20 base To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libseccomp/+bug/1876055/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
