Changeset 931afbc in mainline for kernel/generic/src/ipc/sysipc.c

Timestamp:

2018-06-09T08:41:53Z (7 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

ec39720

Parents:

75701004

Message:

Don't republish call capability on forward failure

When forwarding of a call fails for some reason, the kernel
automatically answers the forwarded call with EFORWARD. It must not
republish the capability because only unanswered calls are associated
with a capability (so that they can be forwarded or answered).
Republishing the capability makes it possible for userspace to attempt
to answer such a call again, which results in kernel panic due to a
failed assertion. As an interesting fact, uspace functions
async_data_read_forward_fast and async_data_write_forward_fast do this.

Also, the motivation behind republishing the capability as explained
by the removed comment turns out to be invalid because such a call
ends up among the original caller's answers.

File:

• kernel/generic/src/ipc/sysipc.c (modified) (3 diffs)

kernel/generic/src/ipc/sysipc.c

@@ -552 +552 @@
                 ipc_answer(&TASK->answerbox, call);
 
-        /* Republish the capability so that the call does not get lost. */
-        cap_publish(TASK, chandle, ckobj);
+        cap_free(TASK, chandle);
+        kobject_put(ckobj);
 
         if (pkobj)
@@ -642 +642 @@
 
         call_t *call = kobj->call;
+        assert(!(call->flags & IPC_CALL_ANSWERED));
 
         ipc_data_t saved_data;
@@ -688 +689 @@
 
         call_t *call = kobj->call;
+        assert(!(call->flags & IPC_CALL_ANSWERED));
 
         ipc_data_t saved_data;