From: Stephen Smalley <sds@tycho.nsa.gov>
To: Janne Karhunen <janne.karhunen@gmail.com>,
Mimi Zohar <zohar@linux.ibm.com>,
paul@paul-moore.com
Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org
Subject: Re: sleep in selinux_audit_rule_init
Date: Wed, 22 May 2019 08:20:10 -0400 [thread overview]
Message-ID: <e8dcc9a2-594d-f81a-32a7-e18f591c6062@tycho.nsa.gov> (raw)
In-Reply-To: <CAE=NcrYsfQ2ijJJMEyTFoWnFqF2qGS=B2JNsVaE8WUNcGS7D9Q@mail.gmail.com>
On 5/22/19 7:49 AM, Janne Karhunen wrote:
> Hi,
>
> I managed to hit a following BUG, looks like ima can call
> selinux_audit_rule_init that can sleep in rcu critical section in
> ima_match_policy():
>
> __might_sleep
> kmem_cache_alloc_trace
> selinux_audit_rule_init <<< kzalloc (.. GFP_KERNEL)
> security_audit_rule_init
> ima_match_policy <<< list_for_each_entry_rcu
> ima_get_action
> process_measurement
> ima_file_check
> path_openat
> do_filp_open
> ..
>
> I guess this is the ima_match_rules() calling ima_lsm_update_rules()
> when it concludes that the selinux policy may have been reloaded.
>
> The easy way for me to fix my own butt in this regard is to change the
> selinux allocation not to wait, but Paul would you be OK with such
> change? The alternative looks like a pretty big change in the ima?
This is perhaps a sign of a deeper bug in IMA; if they are in the middle
of matching against their policy rules, then they shouldn't be
updating/modifying those rules in the middle of match processing? How
is that safe under RCU?
If you look at how the audit subsystem deals with the same problem, they
have a callback (audit_update_lsm_rules) that is called upon an AVC
reset (hence upon a policy reload) and can update all of their rules at
that time, not lazily during matching. Since that time, a more general
notifier mechanism was added, register_lsm_notifier(), and is used by
infiniband to update its state upon policy changes.
next prev parent reply other threads:[~2019-05-22 12:20 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 11:49 sleep in selinux_audit_rule_init Janne Karhunen
2019-05-22 12:20 ` Stephen Smalley [this message]
2019-05-22 12:41 ` Stephen Smalley
2019-05-22 13:00 ` Mimi Zohar
2019-05-22 13:16 ` Stephen Smalley
2019-05-22 13:57 ` Mimi Zohar
2019-05-22 15:10 ` Casey Schaufler
2019-05-22 15:27 ` Stephen Smalley
2019-05-30 10:39 ` Janne Karhunen
2019-05-30 12:07 ` Stephen Smalley
2019-05-30 12:29 ` Paul Moore
2019-05-30 13:27 ` Janne Karhunen
2019-05-30 14:17 ` Stephen Smalley
2019-05-31 11:22 ` Janne Karhunen
2019-05-22 12:47 ` Janne Karhunen
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