linux-kernel - Re: [PATCH v4 09/11] smack: namespace groundwork

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Date:	Thu, 15 Oct 2015 14:53:22 +0200
From:	Lukasz Pawelczyk <l.pawelczyk@...sung.com>
To:	Hillf Danton <hillf.zj@...baba-inc.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Kees Cook <keescook@...omium.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH v4 09/11] smack: namespace groundwork

On czw, 2015-10-15 at 14:41 +0200, Lukasz Pawelczyk wrote:

> No, not a typo. A regular bug. Thanks for spotting it. Also sync
> mechanism before freeing was missing:


Hitfix, will be integrated with the next respin:

diff --git a/security/smack/smack.h b/security/smack/smack.h
index 3d432f4..3a795bf 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -97,6 +97,7 @@ struct smack_ns {
 struct smack_known_ns {
        struct list_head        smk_list_known;
        struct list_head        smk_list_ns;
+       struct rcu_head         smk_rcu;
        struct user_namespace   *smk_ns;
        char                    *smk_mapped;
        struct smack_known      *smk_unmapped;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 8e0da67..234da71 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4669,6 +4669,15 @@ static inline int smack_userns_create(struct user_namespace *ns)
        return 0;
 }
 
+static void smk_free_known_ns(struct rcu_head *head)
+{
+       struct smack_known_ns *sknp = container_of(head, struct smack_known_ns, smk_rcu);
+
+       if (sknp->smk_allocated)
+               kfree(sknp->smk_mapped);
+       kfree(sknp);
+}
+
 static inline void smack_userns_free(struct user_namespace *ns)
 {
        struct smack_ns *snsp = ns->security;
@@ -4680,12 +4689,11 @@ static inline void smack_userns_free(struct user_namespace *ns)
 
                mutex_lock(&skp->smk_mapped_lock);
                list_del_rcu(&sknp->smk_list_known);
-               if (sknp->smk_allocated)
-                       kfree(sknp->smk_mapped);
-               kfree(sknp);
                mutex_unlock(&skp->smk_mapped_lock);
 
                list_del(&sknp->smk_list_ns);
+
+               call_rcu(&sknp->smk_rcu, smk_free_known_ns);
        }
 
        kfree(snsp);
-- 



-- 
Lukasz Pawelczyk
Samsung R&D Institute Poland
Samsung Electronics




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