On 24/05/2023 17:38, Mickaël Salaün wrote:
On 23/05/2023 23:12, Paul Moore wrote:
On Tue, May 23, 2023 at 2:13 AM Jeff Xu <jeffxu@xxxxxxxxxxxx> wrote:
On Mon, May 22, 2023 at 12:56 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
On Thu, May 18, 2023 at 5:26 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:
On 5/18/2023 1:45 PM, Shervin Oloumi wrote:
Adds a new getprocattr hook function to the Landlock LSM, which tracks
the landlocked state of the process. This is invoked when user-space
reads /proc/[pid]/attr/domain
Please don't add a Landlock specific entry directly in the attr/
directory. Add it only to attr/landlock.
Also be aware that the LSM maintainer (Paul Moore) wants to move
away from the /proc/.../attr interfaces in favor of a new system call,
which is in review.
What Casey said above.
There is still some uncertainty around timing, and if we're perfectly
honest, acceptance of the new syscalls at the Linus level, but yes, I
would very much like to see the LSM infrastructure move away from
procfs and towards a syscall API. Part of the reasoning is that the
current procfs API is ill-suited to handle the multiple, stacked LSMs
and the other part being the complexity of procfs in a namespaced
system. If the syscall API is ultimately rejected, we will need to
revisit the idea of a procfs API, but even then I think we'll need to
make some changes to the current approach.
As I believe we are in the latter stages of review for the syscall
API, perhaps you could take a look and ensure that the current
proposed API works for what you are envisioning with Landlock?
I agree, and since the LSM syscalls are almost ready that should not
change much the timing. In fact, extending these syscalls might be
easier than tweaking the current procfs/attr API for Landlock specific
requirements (e.g. scoped visibility). We should ensure that these
syscalls would be a good fit to return file descriptors, but in the
short term we only need to know if a process is landlocked or not, so a
raw return value (0 or -errno) will be enough.
Mentioning in the LSM syscalls patch series that they may deal with (and
return) file descriptors could help API reviewers though.
It should be kept in mind that the current LSM syscalls only deal with
the calling task, whereas the goal of this Landlock patch series is to
inspect other tasks. A new LSM syscall would need to be created to
handle pidfd e.g., named lsm_get_proc_attr() or lsm_get_pid_attr().
I'm not sure if this should be a generic LSM syscall or a Landlock
syscall though. I have plan to handle processes other than the caller
(e.g. to restrict an existing process hierarchy), so thinking about a
Landlock-specific syscall could make sense.
To summarize, creating a new LSM syscall to deal with pidfd and to get
LSM process "status/attr" looks OK. However, Landlock-specific syscalls
to deal with Landlock specificities (e.g. ruleset or domain file
descriptor) make more sense.
Having one LSM-generic syscall to get minimal Landlock attributes (i.e.
mainly to know if a process is sandboxed), and another Landlock-specific
syscall to do more things (e.g. get the domain file descriptor, restrict
a task) seems reasonable. The second one would overlap with the first
one though. What do you think?
