5 files changed, 89 insertions, 17 deletions

diff --git a/Documentation/keys.txt b/Documentation/keys.txt
index 703020012708..3bbe157b45e4 100644
--- a/Documentation/keys.txt
+++ b/Documentation/keys.txt
@@ -964,6 +964,16 @@ The structure has a number of fields, some of which are mandatory:
      It is not safe to sleep in this method; the caller may hold spinlocks.
 
 
+ (*) void (*revoke)(struct key *key);
+
+     This method is optional.  It is called to discard part of the payload
+     data upon a key being revoked.  The caller will have the key semaphore
+     write-locked.
+
+     It is safe to sleep in this method, though care should be taken to avoid
+     a deadlock against the key semaphore.
+
+
  (*) void (*destroy)(struct key *key);
 
      This method is optional. It is called to discard the payload data on a key
diff --git a/include/linux/key.h b/include/linux/key.h
index 8c275d12ef63..e81ebf910d0b 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -205,6 +205,11 @@ struct key_type {
         /* match a key against a description */
         int (*match)(const struct key *key, const void *desc);
 
+        /* clear some of the data from a key on revokation (optional)
+         * - the key's semaphore will be write-locked by the caller
+         */
+        void (*revoke)(struct key *key);
+
         /* clear the data from a key (optional) */
         void (*destroy)(struct key *key);
 
diff --git a/security/keys/key.c b/security/keys/key.c
index 14a15abb7735..51f851557389 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -907,6 +907,10 @@ void key_revoke(struct key *key)
          * it */
         down_write(&key->sem);
         set_bit(KEY_FLAG_REVOKED, &key->flags);
+
+        if (key->type->revoke)
+                key->type->revoke(key);
+
         up_write(&key->sem);
 
 } /* end key_revoke() */
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index a50a91332fe1..4d9825f9962c 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -391,6 +391,8 @@ key_ref_t search_process_keyrings(struct key_type *type,
         struct request_key_auth *rka;
         key_ref_t key_ref, ret, err;
 
+        might_sleep();
+
         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
          * searchable, but we failed to find a key or we found a negative key;
          * otherwise we want to return a sample error (probably -EACCES) if
@@ -496,27 +498,35 @@ key_ref_t search_process_keyrings(struct key_type *type,
          */
         if (context->request_key_auth &&
             context == current &&
-            type != &key_type_request_key_auth &&
-            key_validate(context->request_key_auth) == 0
+            type != &key_type_request_key_auth
             ) {
-                rka = context->request_key_auth->payload.data;
+                /* defend against the auth key being revoked */
+                down_read(&context->request_key_auth->sem);
 
-                key_ref = search_process_keyrings(type, description, match,
-                                                  rka->context);
+                if (key_validate(context->request_key_auth) == 0) {
+                        rka = context->request_key_auth->payload.data;
 
-                if (!IS_ERR(key_ref))
-                        goto found;
+                        key_ref = search_process_keyrings(type, description,
+                                                          match, rka->context);
 
-                switch (PTR_ERR(key_ref)) {
-                case -EAGAIN: /* no key */
-                        if (ret)
+                        up_read(&context->request_key_auth->sem);
+
+                        if (!IS_ERR(key_ref))
+                                goto found;
+
+                        switch (PTR_ERR(key_ref)) {
+                        case -EAGAIN: /* no key */
+                                if (ret)
+                                        break;
+                        case -ENOKEY: /* negative key */
+                                ret = key_ref;
                                 break;
-                case -ENOKEY: /* negative key */
-                        ret = key_ref;
-                        break;
-                default:
-                        err = key_ref;
-                        break;
+                        default:
+                                err = key_ref;
+                                break;
+                        }
+                } else {
+                        up_read(&context->request_key_auth->sem);
                 }
         }
 
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index 0ecc2e8d2bd0..cb9817ced3fd 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -20,6 +20,7 @@
 
 static int request_key_auth_instantiate(struct key *, const void *, size_t);
 static void request_key_auth_describe(const struct key *, struct seq_file *);
+static void request_key_auth_revoke(struct key *);
 static void request_key_auth_destroy(struct key *);
 static long request_key_auth_read(const struct key *, char __user *, size_t);
 
@@ -31,6 +32,7 @@ struct key_type key_type_request_key_auth = {
         .def_datalen    = sizeof(struct request_key_auth),
         .instantiate    = request_key_auth_instantiate,
         .describe       = request_key_auth_describe,
+        .revoke         = request_key_auth_revoke,
         .destroy        = request_key_auth_destroy,
         .read           = request_key_auth_read,
 };
@@ -93,6 +95,24 @@ static long request_key_auth_read(const struct key *key,
 
 /*****************************************************************************/
 /*
+ * handle revocation of an authorisation token key
+ * - called with the key sem write-locked
+ */
+static void request_key_auth_revoke(struct key *key)
+{
+        struct request_key_auth *rka = key->payload.data;
+
+        kenter("{%d}", key->serial);
+
+        if (rka->context) {
+                put_task_struct(rka->context);
+                rka->context = NULL;
+        }
+
+} /* end request_key_auth_revoke() */
+
+/*****************************************************************************/
+/*
  * destroy an instantiation authorisation token key
  */
 static void request_key_auth_destroy(struct key *key)
@@ -101,6 +121,11 @@ static void request_key_auth_destroy(struct key *key)
 
         kenter("{%d}", key->serial);
 
+        if (rka->context) {
+                put_task_struct(rka->context);
+                rka->context = NULL;
+        }
+
         key_put(rka->target_key);
         kfree(rka);
 
@@ -131,14 +156,26 @@ struct key *request_key_auth_new(struct key *target, const char *callout_info)
          * another process */
         if (current->request_key_auth) {
                 /* it is - use that instantiation context here too */
+                down_read(&current->request_key_auth->sem);
+
+                /* if the auth key has been revoked, then the key we're
+                 * servicing is already instantiated */
+                if (test_bit(KEY_FLAG_REVOKED,
+                             &current->request_key_auth->flags))
+                        goto auth_key_revoked;
+
                 irka = current->request_key_auth->payload.data;
                 rka->context = irka->context;
                 rka->pid = irka->pid;
+                get_task_struct(rka->context);
+
+                up_read(&current->request_key_auth->sem);
         }
         else {
                 /* it isn't - use this process as the context */
                 rka->context = current;
                 rka->pid = current->pid;
+                get_task_struct(rka->context);
         }
 
         rka->target_key = key_get(target);
@@ -161,9 +198,15 @@ struct key *request_key_auth_new(struct key *target, const char *callout_info)
         if (ret < 0)
                 goto error_inst;
 
-        kleave(" = {%d})", authkey->serial);
+        kleave(" = {%d}", authkey->serial);
         return authkey;
 
+auth_key_revoked:
+        up_read(&current->request_key_auth->sem);
+        kfree(rka);
+        kleave("= -EKEYREVOKED");
+        return ERR_PTR(-EKEYREVOKED);
+
 error_inst:
         key_revoke(authkey);
         key_put(authkey);