netdev - [PATCH] cipso,calipso: resolve a number of problems with the DOI refcounts

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Date:   Thu, 04 Mar 2021 16:29:51 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     netdev@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH] cipso,calipso: resolve a number of problems with the DOI
 refcounts

The current CIPSO and CALIPSO refcounting scheme for the DOI
definitions is a bit flawed in that we:

1. Don't correctly match gets/puts in netlbl_cipsov4_list().
2. Decrement the refcount on each attempt to remove the DOI from the
   DOI list, only removing it from the list once the refcount drops
   to zero.

This patch fixes these problems by adding the missing "puts" to
netlbl_cipsov4_list() and introduces a more conventional, i.e.
not-buggy, refcounting mechanism to the DOI definitions.  Upon the
addition of a DOI to the DOI list, it is initialized with a refcount
of one, removing a DOI from the list removes it from the list and
drops the refcount by one; "gets" and "puts" behave as expected with
respect to refcounts, increasing and decreasing the DOI's refcount by
one.

Fixes: b1edeb102397 ("netlabel: Replace protocol/NetLabel linking with refrerence counts")
Fixes: d7cce01504a0 ("netlabel: Add support for removing a CALIPSO DOI.")
Reported-by: syzbot+9ec037722d2603a9f52e@...kaller.appspotmail.com
Signed-off-by: Paul Moore <paul@...l-moore.com>
---
 net/ipv4/cipso_ipv4.c            |   11 +----------
 net/ipv6/calipso.c               |   14 +++++---------
 net/netlabel/netlabel_cipso_v4.c |    3 +++
 3 files changed, 9 insertions(+), 19 deletions(-)

diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 471d33a0d095..be09c7669a79 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -519,16 +519,10 @@ int cipso_v4_doi_remove(u32 doi, struct netlbl_audit *audit_info)
 		ret_val = -ENOENT;
 		goto doi_remove_return;
 	}
-	if (!refcount_dec_and_test(&doi_def->refcount)) {
-		spin_unlock(&cipso_v4_doi_list_lock);
-		ret_val = -EBUSY;
-		goto doi_remove_return;
-	}
 	list_del_rcu(&doi_def->list);
 	spin_unlock(&cipso_v4_doi_list_lock);
 
-	cipso_v4_cache_invalidate();
-	call_rcu(&doi_def->rcu, cipso_v4_doi_free_rcu);
+	cipso_v4_doi_putdef(doi_def);
 	ret_val = 0;
 
 doi_remove_return:
@@ -585,9 +579,6 @@ void cipso_v4_doi_putdef(struct cipso_v4_doi *doi_def)
 
 	if (!refcount_dec_and_test(&doi_def->refcount))
 		return;
-	spin_lock(&cipso_v4_doi_list_lock);
-	list_del_rcu(&doi_def->list);
-	spin_unlock(&cipso_v4_doi_list_lock);
 
 	cipso_v4_cache_invalidate();
 	call_rcu(&doi_def->rcu, cipso_v4_doi_free_rcu);
diff --git a/net/ipv6/calipso.c b/net/ipv6/calipso.c
index 51184a70ac7e..1578ed9e97d8 100644
--- a/net/ipv6/calipso.c
+++ b/net/ipv6/calipso.c
@@ -83,6 +83,9 @@ struct calipso_map_cache_entry {
 
 static struct calipso_map_cache_bkt *calipso_cache;
 
+static void calipso_cache_invalidate(void);
+static void calipso_doi_putdef(struct calipso_doi *doi_def);
+
 /* Label Mapping Cache Functions
  */
 
@@ -444,15 +447,10 @@ static int calipso_doi_remove(u32 doi, struct netlbl_audit *audit_info)
 		ret_val = -ENOENT;
 		goto doi_remove_return;
 	}
-	if (!refcount_dec_and_test(&doi_def->refcount)) {
-		spin_unlock(&calipso_doi_list_lock);
-		ret_val = -EBUSY;
-		goto doi_remove_return;
-	}
 	list_del_rcu(&doi_def->list);
 	spin_unlock(&calipso_doi_list_lock);
 
-	call_rcu(&doi_def->rcu, calipso_doi_free_rcu);
+	calipso_doi_putdef(doi_def);
 	ret_val = 0;
 
 doi_remove_return:
@@ -508,10 +506,8 @@ static void calipso_doi_putdef(struct calipso_doi *doi_def)
 
 	if (!refcount_dec_and_test(&doi_def->refcount))
 		return;
-	spin_lock(&calipso_doi_list_lock);
-	list_del_rcu(&doi_def->list);
-	spin_unlock(&calipso_doi_list_lock);
 
+	calipso_cache_invalidate();
 	call_rcu(&doi_def->rcu, calipso_doi_free_rcu);
 }
 
diff --git a/net/netlabel/netlabel_cipso_v4.c b/net/netlabel/netlabel_cipso_v4.c
index 726dda95934c..4f50a64315cf 100644
--- a/net/netlabel/netlabel_cipso_v4.c
+++ b/net/netlabel/netlabel_cipso_v4.c
@@ -575,6 +575,7 @@ static int netlbl_cipsov4_list(struct sk_buff *skb, struct genl_info *info)
 
 		break;
 	}
+	cipso_v4_doi_putdef(doi_def);
 	rcu_read_unlock();
 
 	genlmsg_end(ans_skb, data);
@@ -583,12 +584,14 @@ static int netlbl_cipsov4_list(struct sk_buff *skb, struct genl_info *info)
 list_retry:
 	/* XXX - this limit is a guesstimate */
 	if (nlsze_mult < 4) {
+		cipso_v4_doi_putdef(doi_def);
 		rcu_read_unlock();
 		kfree_skb(ans_skb);
 		nlsze_mult *= 2;
 		goto list_start;
 	}
 list_failure_lock:
+	cipso_v4_doi_putdef(doi_def);
 	rcu_read_unlock();
 list_failure:
 	kfree_skb(ans_skb);