1 files changed, 148 insertions, 97 deletions

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index e2ab4f8e7481..c9a5de197487 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -132,10 +132,17 @@ static int keyring_duplicate(struct key *keyring, const struct key *source)
                 (PAGE_SIZE - sizeof(*klist)) / sizeof(struct key);
 
         ret = 0;
-        sklist = source->payload.subscriptions;
 
-        if (sklist && sklist->nkeys > 0) {
+        /* find out how many keys are currently linked */
+        rcu_read_lock();
+        sklist = rcu_dereference(source->payload.subscriptions);
+        max = 0;
+        if (sklist)
                 max = sklist->nkeys;
+        rcu_read_unlock();
+
+        /* allocate a new payload and stuff load with key links */
+        if (max > 0) {
                 BUG_ON(max > limit);
 
                 max = (max + 3) & ~3;
@@ -148,6 +155,10 @@ static int keyring_duplicate(struct key *keyring, const struct key *source)
                 if (!klist)
                         goto error;
 
+                /* set links */
+                rcu_read_lock();
+                sklist = rcu_dereference(source->payload.subscriptions);
+
                 klist->maxkeys = max;
                 klist->nkeys = sklist->nkeys;
                 memcpy(klist->keys,
@@ -157,7 +168,9 @@ static int keyring_duplicate(struct key *keyring, const struct key *source)
                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
                         atomic_inc(&klist->keys[loop]->usage);
 
-                keyring->payload.subscriptions = klist;
+                rcu_read_unlock();
+
+                rcu_assign_pointer(keyring->payload.subscriptions, klist);
                 ret = 0;
         }
 
@@ -192,7 +205,7 @@ static void keyring_destroy(struct key *keyring)
                 write_unlock(&keyring_name_lock);
         }
 
-        klist = keyring->payload.subscriptions;
+        klist = rcu_dereference(keyring->payload.subscriptions);
         if (klist) {
                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
                         key_put(klist->keys[loop]);
@@ -216,17 +229,20 @@ static void keyring_describe(const struct key *keyring, struct seq_file *m)
                 seq_puts(m, "[anon]");
         }
 
-        klist = keyring->payload.subscriptions;
+        rcu_read_lock();
+        klist = rcu_dereference(keyring->payload.subscriptions);
         if (klist)
                 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
         else
                 seq_puts(m, ": empty");
+        rcu_read_unlock();
 
 } /* end keyring_describe() */
 
 /*****************************************************************************/
 /*
  * read a list of key IDs from the keyring's contents
+ * - the keyring's semaphore is read-locked
  */
 static long keyring_read(const struct key *keyring,
                          char __user *buffer, size_t buflen)
@@ -237,7 +253,7 @@ static long keyring_read(const struct key *keyring,
         int loop, ret;
 
         ret = 0;
-        klist = keyring->payload.subscriptions;
+        klist = rcu_dereference(keyring->payload.subscriptions);
 
         if (klist) {
                 /* calculate how much data we could return */
@@ -320,7 +336,7 @@ struct key *keyring_search_aux(struct key *keyring,
                                key_match_func_t match)
 {
         struct {
-                struct key *keyring;
+                struct keyring_list *keylist;
                 int kix;
         } stack[KEYRING_SEARCH_MAX_DEPTH];
 
@@ -328,10 +344,12 @@ struct key *keyring_search_aux(struct key *keyring,
         struct timespec now;
         struct key *key;
         long err;
-        int sp, psp, kix;
+        int sp, kix;
 
         key_check(keyring);
 
+        rcu_read_lock();
+
         /* top keyring must have search permission to begin the search */
         key = ERR_PTR(-EACCES);
         if (!key_permission(keyring, KEY_SEARCH))
@@ -347,11 +365,10 @@ struct key *keyring_search_aux(struct key *keyring,
 
         /* start processing a new keyring */
  descend:
-        read_lock(&keyring->lock);
-        if (keyring->flags & KEY_FLAG_REVOKED)
+        if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
                 goto not_this_keyring;
 
-        keylist = keyring->payload.subscriptions;
+        keylist = rcu_dereference(keyring->payload.subscriptions);
         if (!keylist)
                 goto not_this_keyring;
 
@@ -364,7 +381,7 @@ struct key *keyring_search_aux(struct key *keyring,
                         continue;
 
                 /* skip revoked keys and expired keys */
-                if (key->flags & KEY_FLAG_REVOKED)
+                if (test_bit(KEY_FLAG_REVOKED, &key->flags))
                         continue;
 
                 if (key->expiry && now.tv_sec >= key->expiry)
@@ -379,7 +396,7 @@ struct key *keyring_search_aux(struct key *keyring,
                         continue;
 
                 /* we set a different error code if we find a negative key */
-                if (key->flags & KEY_FLAG_NEGATIVE) {
+                if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
                         err = -ENOKEY;
                         continue;
                 }
@@ -390,48 +407,37 @@ struct key *keyring_search_aux(struct key *keyring,
         /* search through the keyrings nested in this one */
         kix = 0;
  ascend:
-        while (kix < keylist->nkeys) {
+        for (; kix < keylist->nkeys; kix++) {
                 key = keylist->keys[kix];
                 if (key->type != &key_type_keyring)
-                        goto next;
+                        continue;
 
                 /* recursively search nested keyrings
                  * - only search keyrings for which we have search permission
                  */
                 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
-                        goto next;
+                        continue;
 
                 if (!key_permission(key, KEY_SEARCH))
-                        goto next;
-
-                /* evade loops in the keyring tree */
-                for (psp = 0; psp < sp; psp++)
-                        if (stack[psp].keyring == keyring)
-                                goto next;
+                        continue;
 
                 /* stack the current position */
-                stack[sp].keyring = keyring;
+                stack[sp].keylist = keylist;
                 stack[sp].kix = kix;
                 sp++;
 
                 /* begin again with the new keyring */
                 keyring = key;
                 goto descend;
-
-        next:
-                kix++;
         }
 
         /* the keyring we're looking at was disqualified or didn't contain a
          * matching key */
  not_this_keyring:
-        read_unlock(&keyring->lock);
-
         if (sp > 0) {
                 /* resume the processing of a keyring higher up in the tree */
                 sp--;
-                keyring = stack[sp].keyring;
-                keylist = keyring->payload.subscriptions;
+                keylist = stack[sp].keylist;
                 kix = stack[sp].kix + 1;
                 goto ascend;
         }
@@ -442,16 +448,9 @@ struct key *keyring_search_aux(struct key *keyring,
         /* we found a viable match */
  found:
         atomic_inc(&key->usage);
-        read_unlock(&keyring->lock);
-
-        /* unwind the keyring stack */
-        while (sp > 0) {
-                sp--;
-                read_unlock(&stack[sp].keyring->lock);
-        }
-
         key_check(key);
  error:
+        rcu_read_unlock();
         return key;
 
 } /* end keyring_search_aux() */
@@ -489,7 +488,9 @@ struct key *__keyring_search_one(struct key *keyring,
         struct key *key;
         int loop;
 
-        klist = keyring->payload.subscriptions;
+        rcu_read_lock();
+
+        klist = rcu_dereference(keyring->payload.subscriptions);
         if (klist) {
                 for (loop = 0; loop < klist->nkeys; loop++) {
                         key = klist->keys[loop];
@@ -497,7 +498,7 @@ struct key *__keyring_search_one(struct key *keyring,
                         if (key->type == ktype &&
                             key->type->match(key, description) &&
                             key_permission(key, perm) &&
-                            !(key->flags & KEY_FLAG_REVOKED)
+                            !test_bit(KEY_FLAG_REVOKED, &key->flags)
                             )
                                 goto found;
                 }
@@ -509,6 +510,7 @@ struct key *__keyring_search_one(struct key *keyring,
  found:
         atomic_inc(&key->usage);
  error:
+        rcu_read_unlock();
         return key;
 
 } /* end __keyring_search_one() */
@@ -540,7 +542,7 @@ struct key *find_keyring_by_name(const char *name, key_serial_t bound)
                                     &keyring_name_hash[bucket],
                                     type_data.link
                                     ) {
-                        if (keyring->flags & KEY_FLAG_REVOKED)
+                        if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
                                 continue;
 
                         if (strcmp(keyring->description, name) != 0)
@@ -579,7 +581,7 @@ struct key *find_keyring_by_name(const char *name, key_serial_t bound)
 static int keyring_detect_cycle(struct key *A, struct key *B)
 {
         struct {
-                struct key *subtree;
+                struct keyring_list *keylist;
                 int kix;
         } stack[KEYRING_SEARCH_MAX_DEPTH];
 
@@ -587,20 +589,21 @@ static int keyring_detect_cycle(struct key *A, struct key *B)
         struct key *subtree, *key;
         int sp, kix, ret;
 
+        rcu_read_lock();
+
         ret = -EDEADLK;
         if (A == B)
-                goto error;
+                goto cycle_detected;
 
         subtree = B;
         sp = 0;
 
         /* start processing a new keyring */
  descend:
-        read_lock(&subtree->lock);
-        if (subtree->flags & KEY_FLAG_REVOKED)
+        if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
                 goto not_this_keyring;
 
-        keylist = subtree->payload.subscriptions;
+        keylist = rcu_dereference(subtree->payload.subscriptions);
         if (!keylist)
                 goto not_this_keyring;
         kix = 0;
@@ -619,7 +622,7 @@ static int keyring_detect_cycle(struct key *A, struct key *B)
                                 goto too_deep;
 
                         /* stack the current position */
-                        stack[sp].subtree = subtree;
+                        stack[sp].keylist = keylist;
                         stack[sp].kix = kix;
                         sp++;
 
@@ -632,13 +635,10 @@ static int keyring_detect_cycle(struct key *A, struct key *B)
         /* the keyring we're looking at was disqualified or didn't contain a
          * matching key */
  not_this_keyring:
-        read_unlock(&subtree->lock);
-
         if (sp > 0) {
                 /* resume the checking of a keyring higher up in the tree */
                 sp--;
-                subtree = stack[sp].subtree;
-                keylist = subtree->payload.subscriptions;
+                keylist = stack[sp].keylist;
                 kix = stack[sp].kix + 1;
                 goto ascend;
         }
@@ -646,30 +646,36 @@ static int keyring_detect_cycle(struct key *A, struct key *B)
         ret = 0; /* no cycles detected */
 
  error:
+        rcu_read_unlock();
         return ret;
 
  too_deep:
         ret = -ELOOP;
-        goto error_unwind;
+        goto error;
+
  cycle_detected:
         ret = -EDEADLK;
- error_unwind:
-        read_unlock(&subtree->lock);
-
-        /* unwind the keyring stack */
-        while (sp > 0) {
-                sp--;
-                read_unlock(&stack[sp].subtree->lock);
-        }
-
         goto error;
 
 } /* end keyring_detect_cycle() */
 
 /*****************************************************************************/
 /*
+ * dispose of a keyring list after the RCU grace period
+ */
+static void keyring_link_rcu_disposal(struct rcu_head *rcu)
+{
+        struct keyring_list *klist =
+                container_of(rcu, struct keyring_list, rcu);
+
+        kfree(klist);
+
+} /* end keyring_link_rcu_disposal() */
+
+/*****************************************************************************/
+/*
  * link a key into to a keyring
- * - must be called with the keyring's semaphore held
+ * - must be called with the keyring's semaphore write-locked
  */
 int __key_link(struct key *keyring, struct key *key)
 {
@@ -679,7 +685,7 @@ int __key_link(struct key *keyring, struct key *key)
         int ret;
 
         ret = -EKEYREVOKED;
-        if (keyring->flags & KEY_FLAG_REVOKED)
+        if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
                 goto error;
 
         ret = -ENOTDIR;
@@ -710,9 +716,10 @@ int __key_link(struct key *keyring, struct key *key)
                 /* there's sufficient slack space to add directly */
                 atomic_inc(&key->usage);
 
-                write_lock(&keyring->lock);
-                klist->keys[klist->nkeys++] = key;
-                write_unlock(&keyring->lock);
+                klist->keys[klist->nkeys] = key;
+                smp_wmb();
+                klist->nkeys++;
+                smp_wmb();
 
                 ret = 0;
         }
@@ -723,6 +730,8 @@ int __key_link(struct key *keyring, struct key *key)
                         max += klist->maxkeys;
 
                 ret = -ENFILE;
+                if (max > 65535)
+                        goto error3;
                 size = sizeof(*klist) + sizeof(*key) * max;
                 if (size > PAGE_SIZE)
                         goto error3;
@@ -743,14 +752,13 @@ int __key_link(struct key *keyring, struct key *key)
 
                 /* add the key into the new space */
                 atomic_inc(&key->usage);
-
-                write_lock(&keyring->lock);
-                keyring->payload.subscriptions = nklist;
                 nklist->keys[nklist->nkeys++] = key;
-                write_unlock(&keyring->lock);
+
+                rcu_assign_pointer(keyring->payload.subscriptions, nklist);
 
                 /* dispose of the old keyring list */
-                kfree(klist);
+                if (klist)
+                        call_rcu(&klist->rcu, keyring_link_rcu_disposal);
 
                 ret = 0;
         }
@@ -791,11 +799,26 @@ EXPORT_SYMBOL(key_link);
 
 /*****************************************************************************/
 /*
+ * dispose of a keyring list after the RCU grace period, freeing the unlinked
+ * key
+ */
+static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
+{
+        struct keyring_list *klist =
+                container_of(rcu, struct keyring_list, rcu);
+
+        key_put(klist->keys[klist->delkey]);
+        kfree(klist);
+
+} /* end keyring_unlink_rcu_disposal() */
+
+/*****************************************************************************/
+/*
  * unlink the first link to a key from a keyring
  */
 int key_unlink(struct key *keyring, struct key *key)
 {
-        struct keyring_list *klist;
+        struct keyring_list *klist, *nklist;
         int loop, ret;
 
         key_check(keyring);
@@ -819,31 +842,45 @@ int key_unlink(struct key *keyring, struct key *key)
         ret = -ENOENT;
         goto error;
 
- key_is_present:
+key_is_present:
+        /* we need to copy the key list for RCU purposes */
+        nklist = kmalloc(sizeof(*klist) + sizeof(*key) * klist->maxkeys,
+                         GFP_KERNEL);
+        if (!nklist)
+                goto nomem;
+        nklist->maxkeys = klist->maxkeys;
+        nklist->nkeys = klist->nkeys - 1;
+
+        if (loop > 0)
+                memcpy(&nklist->keys[0],
+                       &klist->keys[0],
+                       loop * sizeof(klist->keys[0]));
+
+        if (loop < nklist->nkeys)
+                memcpy(&nklist->keys[loop],
+                       &klist->keys[loop + 1],
+                       (nklist->nkeys - loop) * sizeof(klist->keys[0]));
+
         /* adjust the user's quota */
         key_payload_reserve(keyring,
                             keyring->datalen - KEYQUOTA_LINK_BYTES);
 
-        /* shuffle down the key pointers
-         * - it might be worth shrinking the allocated memory, but that runs
-         *   the risk of ENOMEM as we would have to copy
-         */
-        write_lock(&keyring->lock);
+        rcu_assign_pointer(keyring->payload.subscriptions, nklist);
 
-        klist->nkeys--;
-        if (loop < klist->nkeys)
-                memcpy(&klist->keys[loop],
-                       &klist->keys[loop + 1],
-                       (klist->nkeys - loop) * sizeof(struct key *));
+        up_write(&keyring->sem);
 
-        write_unlock(&keyring->lock);
+        /* schedule for later cleanup */
+        klist->delkey = loop;
+        call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
 
-        up_write(&keyring->sem);
-        key_put(key);
         ret = 0;
 
- error:
+error:
         return ret;
+nomem:
+        ret = -ENOMEM;
+        up_write(&keyring->sem);
+        goto error;
 
 } /* end key_unlink() */
 
@@ -851,13 +888,32 @@ EXPORT_SYMBOL(key_unlink);
 
 /*****************************************************************************/
 /*
+ * dispose of a keyring list after the RCU grace period, releasing the keys it
+ * links to
+ */
+static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
+{
+        struct keyring_list *klist;
+        int loop;
+
+        klist = container_of(rcu, struct keyring_list, rcu);
+
+        for (loop = klist->nkeys - 1; loop >= 0; loop--)
+                key_put(klist->keys[loop]);
+
+        kfree(klist);
+
+} /* end keyring_clear_rcu_disposal() */
+
+/*****************************************************************************/
+/*
  * clear the specified process keyring
  * - implements keyctl(KEYCTL_CLEAR)
  */
 int keyring_clear(struct key *keyring)
 {
         struct keyring_list *klist;
-        int loop, ret;
+        int ret;
 
         ret = -ENOTDIR;
         if (keyring->type == &key_type_keyring) {
@@ -870,20 +926,15 @@ int keyring_clear(struct key *keyring)
                         key_payload_reserve(keyring,
                                             sizeof(struct keyring_list));
 
-                        write_lock(&keyring->lock);
-                        keyring->payload.subscriptions = NULL;
-                        write_unlock(&keyring->lock);
+                        rcu_assign_pointer(keyring->payload.subscriptions,
+                                           NULL);
                 }
 
                 up_write(&keyring->sem);
 
                 /* free the keys after the locks have been dropped */
-                if (klist) {
-                        for (loop = klist->nkeys - 1; loop >= 0; loop--)
-                                key_put(klist->keys[loop]);
-
-                        kfree(klist);
-                }
+                if (klist)
+                        call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
 
                 ret = 0;
         }