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

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

[David Howells]

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@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.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)

[PATCH 2/3] keys: fix trusted/encrypted keys sparse rcu_assign_pointer messages

[David Howells]

From: Mimi Zohar <zohar@linux.vnet.ibm.com>

Define rcu_assign_keypointer(), which uses the key payload.rcudata instead
of payload.data, to resolve the CONFIG_SPARSE_RCU_POINTER message:
"incompatible types in comparison expression (different address spaces)"

Replace the rcu_assign_pointer() calls in encrypted/trusted keys with
rcu_assign_keypointer().

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/linux/key.h                              |    3 +++
 security/keys/encrypted-keys/encrypted.c         |    4 ++--
 security/keys/encrypted-keys/masterkey_trusted.c |    2 ++
 security/keys/trusted.c                          |    4 ++--
 4 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/key.h b/include/linux/key.h
index 183a6af..bfc014c 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -293,6 +293,9 @@ static inline bool key_is_instantiated(const struct key *key)
 	(rcu_dereference_protected((KEY)->payload.rcudata,		\
 				   rwsem_is_locked(&((struct key *)(KEY))->sem)))
 
+#define rcu_assign_keypointer(KEY, PAYLOAD)				\
+	(rcu_assign_pointer((KEY)->payload.rcudata, PAYLOAD))
+
 #ifdef CONFIG_SYSCTL
 extern ctl_table key_sysctls[];
 #endif
diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 41144f7..d91efb6 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -810,7 +810,7 @@ static int encrypted_instantiate(struct key *key, const void *data,
 		goto out;
 	}
 
-	rcu_assign_pointer(key->payload.data, epayload);
+	rcu_assign_keypointer(key, epayload);
 out:
 	kfree(datablob);
 	return ret;
@@ -874,7 +874,7 @@ static int encrypted_update(struct key *key, const void *data, size_t datalen)
 	memcpy(new_epayload->payload_data, epayload->payload_data,
 	       epayload->payload_datalen);
 
-	rcu_assign_pointer(key->payload.data, new_epayload);
+	rcu_assign_keypointer(key, new_epayload);
 	call_rcu(&epayload->rcu, encrypted_rcu_free);
 out:
 	kfree(buf);
diff --git a/security/keys/encrypted-keys/masterkey_trusted.c b/security/keys/encrypted-keys/masterkey_trusted.c
index df87272..8c16c3e 100644
--- a/security/keys/encrypted-keys/masterkey_trusted.c
+++ b/security/keys/encrypted-keys/masterkey_trusted.c
@@ -18,6 +18,8 @@
 #include <linux/module.h>
 #include <linux/err.h>
 #include <keys/trusted-type.h>
+#include <keys/encrypted-type.h>
+#include "encrypted.h"
 
 /*
  * request_trusted_key - request the trusted key
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 0ed5fdf..2d5d041 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -993,7 +993,7 @@ out:
 	kfree(datablob);
 	kfree(options);
 	if (!ret)
-		rcu_assign_pointer(key->payload.data, payload);
+		rcu_assign_keypointer(key, payload);
 	else
 		kfree(payload);
 	return ret;
@@ -1067,7 +1067,7 @@ static int trusted_update(struct key *key, const void *data, size_t datalen)
 			goto out;
 		}
 	}
-	rcu_assign_pointer(key->payload.data, new_p);
+	rcu_assign_keypointer(key, new_p);
 	call_rcu(&p->rcu, trusted_rcu_free);
 out:
 	kfree(datablob);

[PATCH 3/3] encrypted-keys: fix rcu and sparse messages

[David Howells]

From: Mimi Zohar <zohar@linux.vnet.ibm.com>

Enabling CONFIG_PROVE_RCU and CONFIG_SPARSE_RCU_POINTER resulted in
"suspicious rcu_dereference_check() usage!" and "incompatible types
in comparison expression (different address spaces)" messages.

Access the masterkey directly when holding the rwsem.

Changelog v1:
- Use either rcu_read_lock()/rcu_derefence_key()/rcu_read_unlock()
or remove the unnecessary rcu_derefence() - David Howells

Reported-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 security/keys/encrypted-keys/encrypted.c         |    2 +-
 security/keys/encrypted-keys/masterkey_trusted.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index d91efb6..2d1bb8a 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -314,7 +314,7 @@ static struct key *request_user_key(const char *master_desc, u8 **master_key,
 		goto error;
 
 	down_read(&ukey->sem);
-	upayload = rcu_dereference(ukey->payload.data);
+	upayload = ukey->payload.data;
 	*master_key = upayload->data;
 	*master_keylen = upayload->datalen;
 error:
diff --git a/security/keys/encrypted-keys/masterkey_trusted.c b/security/keys/encrypted-keys/masterkey_trusted.c
index 8c16c3e..013f7e5 100644
--- a/security/keys/encrypted-keys/masterkey_trusted.c
+++ b/security/keys/encrypted-keys/masterkey_trusted.c
@@ -39,7 +39,7 @@ struct key *request_trusted_key(const char *trusted_desc,
 		goto error;
 
 	down_read(&tkey->sem);
-	tpayload = rcu_dereference(tkey->payload.data);
+	tpayload = tkey->payload.data;
 	*master_key = tpayload->key;
 	*master_keylen = tpayload->key_len;
 error: