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/gc.c b/security/keys/gc.c
index bf4d8da..a42b455 100644 (file)
--- 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 (file)
--- 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)