Due to a problematic patch back-ported from Linux 6.5 causing interference between EXT4 and iomap code, there's the possibility of a data corruption bug on older kernels -- most notably recent Linux 6.1 LTS point releases that can currently be found in the likes of Debian 12.

A " subtle interaction " between Iomap and EXT4 is being blamed for this possible EXT4 file-system data corruption bug that is found on the likes of Linux 6.1.64 and 6.1.55 point releases. The new Linux 6.1.66 point release already reverts the problematic commit.

The Debian bug report on the matter describes it as "non-serious data loss" so it should be recoverable. But the timing was bad as Debian 12.3 was due to be released with an affected kernel build, so now instead Debian 12.3 has been delayed .

Debian 12 users are recommended against upgrading their systems until the Linux 6.1.66-based kernel image is rolled out to Debian mirrors soon.

This EXT4 data corruption headache comes just days after the out-of-tree OpenZFS file-system was also dealing with its own (and unrelated to this) data corruption bug .