On 2020-01-22 16:28, Paul Moore wrote: > On Tue, Dec 31, 2019 at 2:49 PM Richard Guy Briggs <rgb@xxxxxxxxxx> 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@xxxxxxxxxx> > > Acked-by: Serge Hallyn <serge@xxxxxxxxxx> > > Acked-by: Steve Grubb <sgrubb@xxxxxxxxxx> > > Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > > Reviewed-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx> > > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx> > > --- > > 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. Fair enough. > > + /* if contid is already set, deny */ > > + else if (audit_contid_set(task)) > > + rc = -ECHILD; > > Does -EEXIST make more sense here? Perhaps. I don't feel strongly about it, but none of these error codes were intended for this use and should not overlap with other errors from writing to /proc. > > + 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. This record should be accompanied by a syscall record (and eventually possibly a CONTAINER_ID record of the orchestrator, if it is already in a container). The syscall record has a res= field that already gives this result. > > + return rc; > > +} > > + > > /** > > * audit_log_end - end one audit record > > * @ab: the audit_buffer > > -- > paul moore > www.paul-moore.com > - RGB -- Richard Guy Briggs <rgb@xxxxxxxxxx> Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635
