在 2017/12/28 22:57, Stephen Smalley 写道:
On Sat, Dec 23, 2017 at 3:03 AM, Li Kun <[email protected]
<mailto:[email protected]>> wrote:
Hi all,
When i start a docker container, the runc will call
selinux_setprocattr to set the exec_sid before start the container.
Meanwhile if i use "semodule -i" to load a policy pp, the old
sidtab will be shutdown before switch to the new sidtab, and cause
sidtab_context_to_sid failed with the errno -NOMEM.
Error message:
Dec 14 09:18:18 wuwenming_vudfua_0 docker:
time="2017-12-14T09:18:18.549862564+08:00" level=error
msg="Handler for GET
/v1.23/containers/192.168.0.2:9082/dfs_d:V100R013C11SPC000BCD2/json
<http://192.168.0.2:9082/dfs_d:V100R013C11SPC000BCD2/json>
returned error: No such container:
192.168.0.2:9082/dfs_d:V100R013C11SPC000BCD2
<http://192.168.0.2:9082/dfs_d:V100R013C11SPC000BCD2>"
Dec 14 09:18:18 wuwenming_vudfua_0 kernel: [ 48.463179] SELinux:
security_context_to_sid(system_u:object_r:svirt_sandbox_file_t:s0:c290,c371)
failed for (dev overlay, type overlay) errno=-12
Dec 14 09:18:18 wuwenming_vudfua_0 dbus-daemon: dbus[720]: avc:
received policyload notice (seqno=2)
Dec 14 09:18:18 wuwenming_vudfua_0 dbus[720]: avc: received
policyload notice (seqno=2)
runc semodule
->selinux_setprocattr ->security_load_policy
->security_context_to_sid
->sidtab_shutdown(oldsidtab)
->read_lock(&policy_rwlock); ->sidtab_map(&oldsidtab,
clone_sid, &newsidtab);
->sidtab_context_to_sid
{
....
if (s->next_sid == UINT_MAX || s->shutdown) {
ret = -ENOMEM;
....
}
->read_unlock(&policy_rwlock);
->write_lock_irq(&policy_rwlock);
->"switch to new policydb"
->write_unlock_irq(&policy_rwlock);
I wonder that if this is the intention or a bug?
If it is the intention, what should the application do when it get
-ENOMEM error, to try again?
If it is a bug, may the two options below suitable to solve the issue?
Option1:
use policy_rwlock to protect the "sidtab_shutdown" &
"sidtab_map" , load_policy is rarely to be called after system
bringing up,
so i think it will not impact much on the performance.
Option2:
Use a temp list to store the sid in oldsidtab after it is
shutdown, and deal with it
after cloning the major sids from oldsidtab to newsidtab and
getting the policy_rwlock.
The current logic is intentional. One might argue that a different
error code might be more suitable in this situation (e.g. EAGAIN or
something), but ENOMEM is already a possible error code when loading
policy upon transient OOM conditions, so the caller might have to
retry regardless. The policy write lock must only be held for the
minimal critical section as otherwise all system activity could be
blocked; it is only held when making the new policydb and sidtab
active not during their allocation and setup - ideally it would be
further reduced to a couple of pointer updates. Is this scenario
something you are encountering in actual practice or just a
theoretically possible one?
Thank you very much for your reply.
Yes, we encounter this issue in our implementation.
We have an intertion in our design that we can divide the policy into
several parts to load separately.
So after the red-hat linux bringing up, which has loaded the system
policy db released by redhat, we begin to load the policy released by
our product ,
and meanwhile someone want to start a docker container, and the runc get
an ENOMEM error like i mentioned above.
Should we merge all the policy into the system policy db and just load once?
--
Best Regards
Li Kun
