Trace showing reproducibility using zfs-linux 2.2.2-0ubuntu9 ** Description changed:
SRU Justification [Impact] * 2.2.2-0ubuntu9 has the 6.7 compat series, including https://github.com/openzfs/zfs/commit/db4fc559cc1931b9219e62aa505cd5c51a17b232, but does not include the fix for that commit (affects both pre-6.7 and post-6.7), https://github.com/openzfs/zfs/commit/f0bf7a247dbb030d68c7fd2b5526dd111cc775d0. This manifests for me on the current (6.8.0-40.40~22.04.3) 22.04 HWE kernel as writes to a file resetting atime back to 0 (reads still seem to work as expected though given that state), which of course breaks real-world things (in my case, I can no longer successfully run LLVM's test suite). Thanks to CONFIG_INIT_STACK_ALL_ZERO=y being the default it seems like this isn't a kernel memory disclosure and is instead a deterministic use of 0, so I don't believe this to be a blatant security vulnerability. This also explains the behaviour observed above. This needs fixing in noble, and then propagating back through whatever kernels are pulling in this version, since linux-modules vendors copies of the pre-built DKMS modules, with the current 6.8 HWE kernel using 2.2.2-0ubuntu9 explicitly. [Fix] * Include f0bf7a247dbb: "[PATCH] Linux 6.7 compat: zfs_setattr fix atime update" from upstream ZFS as quilt patch. [Test Case] * Build tested against Noble generic * Ran autopkgktests for regressions, none encountered + * Ran the following test case: + + Using zfs-linux 2.2.2-0ubuntu9 + $ cd /path/to/zfs + $ rm -f foo + $ touch foo + $ stat foo + $ # observe initial access time of 0 since epoch (1970-01-01) + + Using zfs-linux 2.2.2-0ubuntu9.1 + $ cd /path/to/zfs + $ rm -f foo + $ touch foo + $ stat foo + $ # observe initial access time same as modify/change/birth + + Also see results attached as "zfs-bad" and "zfs-good", respectively [Where things could go wrong] * Low chance of regression, isolated instantiation and logic fix. * Addition of time delta check could cause issues during unexpected delay > 2 seconds. ** Attachment added: "zfs-bad" https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/2077487/+attachment/5824618/+files/zfs-bad -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2077487 Title: Broken atime in 2.2.2-0ubuntu9 (noble's version) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2077487/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
