Re: [PATCH ghak90 V8 02/16] audit: add container id

On Tue, Dec 31, 2019 at 2:49 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > Implement the proc fs write to set the audit container identifier of a > process, emitting an AUDIT_CONTAINER_OP record to document the event. > > This is a write from the container orchestrator task to a proc entry of > the form /proc/PID/audit_containerid where PID is the process ID of the > newly created task that is to become the first task in a container, or > an additional task added to a container. > > The write expects up to a u64 value (unset: 18446744073709551615). > > The writer must have capability CAP_AUDIT_CONTROL. > > This will produce a record such as this: > type=CONTAINER_OP msg=audit(2018-06-06 12:39:29.636:26949) : op=set opid=2209 contid=123456 old-contid=18446744073709551615 > > The "op" field indicates an initial set. The "opid" field is the > object's PID, the process being "contained". New and old audit > container identifier values are given in the "contid" fields. > > It is not permitted to unset the audit container identifier. > A child inherits its parent's audit container identifier. > > Please see the github audit kernel issue for the main feature: > https://github.com/linux-audit/audit-kernel/issues/90 > Please see the github audit userspace issue for supporting additions: > https://github.com/linux-audit/audit-userspace/issues/51 > Please see the github audit testsuiite issue for the test case: > https://github.com/linux-audit/audit-testsuite/issues/64 > Please see the github audit wiki for the feature overview: > https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > Acked-by: Serge Hallyn <serge(a)hallyn.com&gt; > Acked-by: Steve Grubb <sgrubb(a)redhat.com&gt; > Acked-by: Neil Horman <nhorman(a)tuxdriver.com&gt; > Reviewed-by: Ondrej Mosnacek <omosnace(a)redhat.com&gt; > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > --- > fs/proc/base.c | 36 ++++++++++++++++++++++++++++ > include/linux/audit.h | 25 ++++++++++++++++++++ > include/uapi/linux/audit.h | 2 ++ > kernel/audit.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++ > kernel/audit.h | 1 + > kernel/auditsc.c | 4 ++++ > 6 files changed, 126 insertions(+) ... > diff --git a/kernel/audit.c b/kernel/audit.c > index 397f8fb4836a..2d7707426b7d 100644 > --- a/kernel/audit.c > +++ b/kernel/audit.c > @@ -2356,6 +2358,62 @@ int audit_signal_info(int sig, struct task_struct *t) > return audit_signal_info_syscall(t); > } > > +/* > + * audit_set_contid - set current task's audit contid > + * @task: target task > + * @contid: contid value > + * > + * Returns 0 on success, -EPERM on permission failure. > + * > + * Called (set) from fs/proc/base.c::proc_contid_write(). > + */ > +int audit_set_contid(struct task_struct *task, u64 contid) > +{ > + u64 oldcontid; > + int rc = 0; > + struct audit_buffer *ab; > + > + task_lock(task); > + /* Can't set if audit disabled */ > + if (!task->audit) { > + task_unlock(task); > + return -ENOPROTOOPT; > + } > + oldcontid = audit_get_contid(task); > + read_lock(&tasklist_lock); > + /* Don't allow the audit containerid to be unset */ > + if (!audit_contid_valid(contid)) > + rc = -EINVAL; > + /* if we don't have caps, reject */ > + else if (!capable(CAP_AUDIT_CONTROL)) > + rc = -EPERM; > + /* if task has children or is not single-threaded, deny */ > + else if (!list_empty(&task->children)) > + rc = -EBUSY; > + else if (!(thread_group_leader(task) && thread_group_empty(task))) > + rc = -EALREADY; [NOTE: there is a bigger issue below which I think is going to require a respin/fixup of this patch so I'm going to take the opportunity to do a bit more bikeshedding ;)] It seems like we could combine both the thread/children checks under a single -EBUSY return value. In both cases the caller should be able to determine if the target process is multi-threaded for has spawned children, yes? FWIW, my motivation for this question is that -EALREADY seems like a poor choice here.

> + /* if contid is already set, deny */ > + else if (audit_contid_set(task)) > + rc = -ECHILD; Does -EEXIST make more sense here?

> + read_unlock(&tasklist_lock); > + if (!rc) > + task->audit->contid = contid; > + task_unlock(task); > + > + if (!audit_enabled) > + return rc; > + > + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_CONTAINER_OP); > + if (!ab) > + return rc; > + > + audit_log_format(ab, > + "op=set opid=%d contid=%llu old-contid=%llu", > + task_tgid_nr(task), contid, oldcontid); > + audit_log_end(ab); Assuming audit is enabled we always emit the record above, even if we were not actually able to set the Audit Container ID (ACID); this seems wrong to me. I think the proper behavior would be to either add a "res=" field to indicate success/failure or only emit the record when we actually change a task's ACID. Considering the impact that the ACID value will potentially have on the audit stream, it seems like always logging the record and including a "res=" field may be the safer choice.

> + return rc; > +} > + > /** > * audit_log_end - end one audit record > * @ab: the audit_buffer -- paul moore www.paul-moore.com