On Wed, Mar 27, 2019 at 9:12 PM Richard Guy Briggs [off-list ref] wrote:
On 2019-03-27 23:42, Ondrej Mosnacek wrote:
quoted
On Fri, Mar 15, 2019 at 7:35 PM Richard Guy Briggs [off-list ref] wrote:
quoted
Audit events could happen in a network namespace outside of a task
context due to packets received from the net that trigger an auditing
rule prior to being associated with a running task. The network
namespace could be in use by multiple containers by association to the
tasks in that network namespace. We still want a way to attribute
these events to any potential containers. Keep a list per network
namespace to track these audit container identifiiers.
Add/increment the audit container identifier on:
- initial setting of the audit container identifier via /proc
- clone/fork call that inherits an audit container identifier
- unshare call that inherits an audit container identifier
- setns call that inherits an audit container identifier
Delete/decrement the audit container identifier on:
- an inherited audit container identifier dropped when child set
- process exit
- unshare call that drops a net namespace
- setns call that drops a net namespace
See: https://github.com/linux-audit/audit-kernel/issues/92
See: https://github.com/linux-audit/audit-testsuite/issues/64
See: https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID
Signed-off-by: Richard Guy Briggs <redacted>
---
include/linux/audit.h | 19 ++++++++++++
kernel/audit.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++--
kernel/nsproxy.c | 4 +++
3 files changed, 106 insertions(+), 3 deletions(-)
diff --git a/include/linux/audit.h b/include/linux/audit.h
index fa19fa408931..70255c2dfb9f 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -27,6 +27,7 @@
#include <linux/ptrace.h>
#include <linux/namei.h> /* LOOKUP_* */
#include <uapi/linux/audit.h>
+#include <linux/refcount.h>
#define AUDIT_INO_UNSET ((unsigned long)-1)
#define AUDIT_DEV_UNSET ((dev_t)-1)
@@ -99,6 +100,13 @@ struct audit_task_info {
extern struct audit_task_info init_struct_audit;
+struct audit_contid {
+ struct list_head list;
+ u64 id;
+ refcount_t refcount;
Hm, since we only ever touch the refcount under a spinlock, I wonder
if we could just make it a regular unsigned int (we don't need the
atomicity guarantees). OTOH, refcount_t comes with some extra overflow
checking, so it's probably better to leave it as is...
Since the update is done using rcu-safe methods, do we even need the
spin_lock? Neil? Paul?
As discussed, the refcount field is protected against simultaneous
writes by the spinlock that protects additions/removals from the list
as a whole so I don't believe the refcount_t atomicity is critical in
this regard.
Where it gets tricky, and I can't say I'm 100% confident on my answer
here, is if refcount was a regular int and we wanted to access it
outside of a spinlock (to be clear, it doesn't look like this patch
currently does this). With RCU, if refcount was a regular int
(unsigned or otherwise), I believe it would be possible for different
threads of execution to potentially see different values of refcount
(assuming one thread was adding/removing from the list). Using a
refcount_t would protect against this, alternatively, taking the
spinlock should also protect against this.
As we all know, RCU can be tricky at times, so I may be off on the
above; if I am, please provide an explanation so I (and likely others
as well) can learn a little bit more. :)
--
paul moore
www.paul-moore.com