linux-kernel - [PATCH 1/3] KEYS: Add missing smp_rmb() primitives to the keyring search code

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120117203940.14882.56709.stgit@warthog.procyon.org.uk>
Date:	Tue, 17 Jan 2012 20:39:40 +0000
From:	David Howells <dhowells@...hat.com>
To:	jmorris@...ei.org
Cc:	keyrings@...ux-nfs.org, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	David Howells <dhowells@...hat.com>
Subject: [PATCH 1/3] KEYS: Add missing smp_rmb() primitives to the keyring
 search code

Add missing smp_rmb() primitives to the keyring search code.

When keyring payloads are appended to without replacement (thus using up spare
slots in the key pointer array), an smp_wmb() is issued between the pointer
assignment and the increment of the key count (nkeys).

There should be corresponding read barriers between the read of nkeys and
dereferences of keys[n] when n is dependent on the value of nkeys.

Signed-off-by: David Howells <dhowells@...hat.com>
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---

 security/keys/gc.c      |    4 +++-
 security/keys/keyring.c |   22 +++++++++++++++-------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/security/keys/gc.c b/security/keys/gc.c
index bf4d8da..a42b455 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -145,7 +145,9 @@ static void key_gc_keyring(struct key *keyring, time_t limit)
 	if (!klist)
 		goto unlock_dont_gc;
 
-	for (loop = klist->nkeys - 1; loop >= 0; loop--) {
+	loop = klist->nkeys;
+	smp_rmb();
+	for (loop--; loop >= 0; loop--) {
 		key = klist->keys[loop];
 		if (test_bit(KEY_FLAG_DEAD, &key->flags) ||
 		    (key->expiry > 0 && key->expiry <= limit))
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 37a7f3b..d605f75 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -319,7 +319,7 @@ key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 	struct key *keyring, *key;
 	key_ref_t key_ref;
 	long err;
-	int sp, kix;
+	int sp, nkeys, kix;
 
 	keyring = key_ref_to_ptr(keyring_ref);
 	possessed = is_key_possessed(keyring_ref);
@@ -380,7 +380,9 @@ descend:
 		goto not_this_keyring;
 
 	/* iterate through the keys in this keyring first */
-	for (kix = 0; kix < keylist->nkeys; kix++) {
+	nkeys = keylist->nkeys;
+	smp_rmb();
+	for (kix = 0; kix < nkeys; kix++) {
 		key = keylist->keys[kix];
 		kflags = key->flags;
 
@@ -421,7 +423,9 @@ descend:
 	/* search through the keyrings nested in this one */
 	kix = 0;
 ascend:
-	for (; kix < keylist->nkeys; kix++) {
+	nkeys = keylist->nkeys;
+	smp_rmb();
+	for (; kix < nkeys; kix++) {
 		key = keylist->keys[kix];
 		if (key->type != &key_type_keyring)
 			continue;
@@ -515,7 +519,7 @@ key_ref_t __keyring_search_one(key_ref_t keyring_ref,
 	struct keyring_list *klist;
 	unsigned long possessed;
 	struct key *keyring, *key;
-	int loop;
+	int nkeys, loop;
 
 	keyring = key_ref_to_ptr(keyring_ref);
 	possessed = is_key_possessed(keyring_ref);
@@ -524,7 +528,9 @@ key_ref_t __keyring_search_one(key_ref_t keyring_ref,
 
 	klist = rcu_dereference(keyring->payload.subscriptions);
 	if (klist) {
-		for (loop = 0; loop < klist->nkeys; loop++) {
+		nkeys = klist->nkeys;
+		smp_rmb();
+		for (loop = 0; loop < nkeys ; loop++) {
 			key = klist->keys[loop];
 
 			if (key->type == ktype &&
@@ -622,7 +628,7 @@ static int keyring_detect_cycle(struct key *A, struct key *B)
 
 	struct keyring_list *keylist;
 	struct key *subtree, *key;
-	int sp, kix, ret;
+	int sp, nkeys, kix, ret;
 
 	rcu_read_lock();
 
@@ -645,7 +651,9 @@ descend:
 
 ascend:
 	/* iterate through the remaining keys in this keyring */
-	for (; kix < keylist->nkeys; kix++) {
+	nkeys = keylist->nkeys;
+	smp_rmb();
+	for (; kix < nkeys; kix++) {
 		key = keylist->keys[kix];
 
 		if (key == A)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/