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@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
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 @@
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 @@
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 @@
/* 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 @@
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 @@
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 @@
struct keyring_list *keylist;
struct key *subtree, *key;
- int sp, kix, ret;
+ int sp, nkeys, kix, ret;
rcu_read_lock();
@@ -645,7 +651,9 @@
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)