On 7/11/23 14:11, Mimi Zohar wrote:
On Tue, 2023-07-11 at 10:59 -0700, Tushar Sugandhi wrote:
Adding Eric to cc.
On 7/7/23 06:00, Mimi Zohar wrote:
Hi Tushar,
On Mon, 2023-07-03 at 14:57 -0700, Tushar Sugandhi wrote:
IMA does not provide a mechanism to allocate memory for IMA log storage
during kexec operation.
The IMA measurement list is currently being carried across kexec, so
obviously a buffer is being allocated for it. IMA not allocating
memory for the measurment list is not the problem statement. Please
concisely provide the problem statement, explaining why IMA needs to
allocate the buffer.
I meant IMA does not provide separate functions to allocate buffer and
populate measurements. Both operations are wrapped in an atomic
ima_dump_measurement_list().
Ok.
As I mentioned in the comment in the cover letter, if there is no such
technical limitation to allocate the buffer and copy the measurements at
kexec ‘execute’ – I will make the necessary code changes and update the
above line in the patch description accordingly.
The "normal" way of making this type of change would be to split the
existing ima_dump_measurement_list() function. Copying the measurement
list would still be named ima_dump_measurement_list(). The other could
be named ima_alloc_kexec_buf(). Both functions initially would be
called.
Sounds good. I will make that change.
I will define ima_alloc_kexec_buf() to allocate memory at kexec 'load'.
And update ima_dump_measurement_list() to only copy the measurements.
Both the functions will be called during kexec 'load'.
And only the updated ima_dump_measurement_list() will be called
during kexec 'execute'.
Please correct me if I misunderstood.
BTW, as discussed elsewhere I am hoping to get clarity on if we can move
everything (memory allocation and copying measurements) to kexec 'execute'.
My current understanding is segment mapping must happen at kexec 'load'.
Hopefully someone on this thread can validate if its true or not.
Eric, besides updating the buffer at kexec execute, is there anything
else that needs to be done (e.g. updating digests)?
I will also wait for his response. :)
The function should handle the scenario where
the kexec load is called multiple times.
Currently the buffer is being freed with the kexec 'unload'. With this
patch IMA is allocating a buffer for the measurement list, which needs
to be freed independently of the kexec 'unload'.
If we end up allocating the buffer at kexec ‘execute’ (which results in
soft boot to next Kernel) – is it technically possible that
kexec ‘unload’ being called after calling kexec ‘execute’?
If not, should I still free the buffer at kexec ‘unload’ in this
scenario?
The question is how to access the buffer once kexec_add_buffer() is
called.
Mimi
