The dm-ima code does not guarantee that the dm_ima_measure_on_* functions will not be called at the same time. Since they modify and free shared memory, this can lead to Use-After-Free errors or garbage measurements. Further, they don't make sure that the state they measure corresponds to the actual device state. For instance if table_load() runs at the same time as do_resume() on a table swap, dm_ima_measure_on_device_resume() can end up thinking the wrong table is active. Or a concurrent dm_hash_rename() and a table swap, can end up with a the new active table still using the old name. This patchset makes sure the the dm-ima function are serialized and report the correct device state.
However, the code is still messier that in could be. This is because it duplicates the current measurement events and format. I would really like to know if that is necessary. Specifically, it currently measures the following dm device and table actions: load clear rename resume remove I don't see the benefit of reporting changes to the inactive table, or resumes where the device does not change state. From the user's point of view, the device is still the same after these events. At the same time, it doesn't measure device creates if no table was loaded, so you can have situations where the the first measurement for a device is a rename or a remove. A more sensible set of actions to measure would be: create table_swap rename remove Also, the measurement format doesn't map well to how dm device's are actually set up, in a way that makes it harder for the code and records extraneous information. First, like I mentioned before, I don't see the benefit of measuring the inactive table. Second, the name, uuid, and major/minor numbers are properties of the device, not it's table (and dm devices can't have partitions, so the minor count will always be 1). I don't see a reason to store and occasinally log this information twice, if there is an active and incative table, and it forces extra coordination between the dm_ima_measure_on_* functions. I'm wondering it we are stuck with the current events and format, now that this has been released? Or could we bump the version, and change what events we measure, and how we format the output? Benjamin Marzinski (10): dm-ima: remove dm_ima_reset_data() dm-ima: remove broken last_target_measured logic dm-ima: Remove status_flags from dm_ima_measure_on_table_load() dm-ima: don't copy the active table to the inactive table dm-ima: Fix UAF errors and measuring incorrect context dm-ima: remove new_map from dm_ima_measure_on_device_clear dm-ima: Fix issues with dm_ima_measure_on_device_rename dm-ima: Handle race between rename and table swap dm-ima: Fail more gracefully in dm_ima_measure_on_* dm-ima: use active table's size if available drivers/md/dm-ima.c | 506 +++++++++++++++++++----------------------- drivers/md/dm-ima.h | 67 ++++-- drivers/md/dm-ioctl.c | 146 +++++++++++- drivers/md/dm.c | 2 +- 4 files changed, 421 insertions(+), 300 deletions(-) -- 2.53.0
