On Wed, 2021-03-24 at 12:58 +0100, Dmitry Vyukov wrote:

On Wed, Mar 24, 2021 at 12:49 PM Mimi Zohar [off-list ref] wrote:

quoted

On Wed, 2021-03-24 at 12:37 +0100, Dmitry Vyukov wrote:

quoted

On Wed, Mar 24, 2021 at 12:21 PM Tetsuo Handa
[off-list ref] wrote:

quoted

On 2021/03/24 20:10, Mimi Zohar wrote:

quoted

On Wed, 2021-03-24 at 19:10 +0900, Tetsuo Handa wrote:

quoted

On 2021/03/24 1:13, Mimi Zohar wrote:

quoted

On Wed, 2021-03-24 at 00:14 +0900, Tetsuo Handa wrote:

quoted

On 2021/03/23 23:47, Mimi Zohar wrote:

quoted

Initially I also questioned making "integrity" an LSM.  Perhaps it's
time to reconsider.   For now, it makes sense to just fix the NULL
pointer dereferencing.

Do we think calling panic() as "fix the NULL pointer dereferencing" ?

Not supplying "integrity" as an "lsm=" option is a user error.  There
are only two options - allow or deny the caller to proceed.   If the
user is expecting the integrity subsystem to be properly working,
returning a NULL and allowing the system to boot (RFC patch version)
does not make sense.   Better to fail early.

What does the "user" mean? Those who load the vmlinux?
Only the "root" user (so called administrators)?
Any users including other than "root" user?

If the user means those who load the vmlinux, that user is explicitly asking
for disabling "integrity" for some reason. In that case, it is a bug if
booting with "integrity" disabled is impossible.

If the user means something other than those who load the vmlinux,
is there a possibility that that user (especially non "root" users) is
allowed to try to use "integrity" ? If processes other than global init
process can try to use "integrity", wouldn't it be a DoS attack vector?
Please explain in the descripotion why calling panic() does not cause
DoS attack vector.

User in this case, is anyone rebooting the system and is intentionally
changing the default values, dropping the "integrity" option on the
boot command line.

OK. Then, I expect that the system boots instead of calling panic().
That user is explicitly asking for disabling "integrity" for some reason.

That was actually my intention. The prebuilt kernel that I use for
things has all LSMs enabled, but then I needed to try some workload
with only 1 specific LSM, so I gave a different lsm= argument.

IMA/EVM is dependent on "integrity".  Was your intention to also
disable IMA and EVM?

I think, yes... or not sure. I was trying to test a bug that requires
a different major LSM and all minor LSMs are presumably irrelevant. I
dropped existing lsm= arg and added something like lsm=apparmor.

quoted

If so, when disabling "integrity", don't load an
IMA policy.

I don't really know what this means. I guess it simply comes from the
image? If so, there was no easy way to avoid loading.

There are a couple of builtin IMA policies, which may be loaded on boot
by specifying on the boot command line "ima_policy=".   Unless the boot
command line "ima_policy=" option is specified, no policy will loaded.

A custom IMA policy may subsequently be loaded, normally in the
initramfs, by echo'ing the file pathname to
/sys/kernel/security/ima/policy.

Mimi