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Message-ID: <20130131043839.GA14726@mail.hallyn.com>
Date: Thu, 31 Jan 2013 04:38:39 +0000
From: "Serge E. Hallyn" <serge@...lyn.com>
To: aris@...hat.com
Cc: linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
Tejun Heo <tj@...nel.org>,
Serge Hallyn <serge.hallyn@...onical.com>
Subject: Re: [PATCH v4 9/9] devcg: propagate local changes down the
hierarchy
Quoting aris@...hat.com (aris@...hat.com):
...
> New exceptions allowing additional access to devices won't be propagated, but
> it'll be possible to add an exception to access all of part of the newly
> allowed device(s).
Is that intended to apply only to only in the DEFAULT_DENY case? If so
that should be made clear. If not,
...
> @@ -515,11 +673,13 @@ memset(&ex, 0, sizeof(ex));
> &parent->exceptions);
> devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
> devcgroup->local.behavior = DEVCG_DEFAULT_ALLOW;
> + rc = propagate_behavior(devcgroup);
> break;
> case DEVCG_DENY:
> dev_exception_clean_all(devcgroup);
> devcgroup->behavior = DEVCG_DEFAULT_DENY;
> devcgroup->local.behavior = DEVCG_DEFAULT_DENY;
> + rc = propagate_behavior(devcgroup);
> break;
> default:
> rc = -EINVAL;
> @@ -610,9 +770,14 @@ case '\0':
> */
> if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
> dev_exception_rm(devcgroup, &ex);
> - return 0;
> + rc = propagate_exception(devcgroup);
Let's say the default in both parent A and child B is ALLOW, and both
have a blacklist entry for "b 8:* rwm". Now I
echo "b 8:* rwm" > A/devices.allow
removing the blacklist entry. Here you are propagating that to the
child B, which I would argue is actually propagating a new allow to
a child. Which you said you wouldn't do.
> + return rc;
> }
> - return dev_exception_add(devcgroup, &ex);
> + rc = dev_exception_add(devcgroup, &ex);
> + if (!rc)
> + /* if a local behavior wasn't explicitely choosen, pick it */
> + devcgroup->local.behavior = devcgroup->behavior;
> + break;
> case DEVCG_DENY:
> /*
> * If the default policy is to deny by default, try to remove
> @@ -621,13 +786,22 @@ return 0;
> */
> if (devcgroup->behavior == DEVCG_DEFAULT_DENY) {
> dev_exception_rm(devcgroup, &ex);
> - return 0;
> + rc = propagate_exception(devcgroup);
> + return rc;
> }
> - return dev_exception_add(devcgroup, &ex);
> + rc = dev_exception_add(devcgroup, &ex);
> + if (rc)
> + return rc;
> + /* we only propagate new restrictions */
> + rc = propagate_exception(devcgroup);
> + if (!rc)
> + /* if a local behavior wasn't explicitely choosen, pick it */
> + devcgroup->local.behavior = devcgroup->behavior;
> + break;
--
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