pool: pre-reserve pool-memory on pool owner

We must not use VM_NORESERVE, otherwise, memory is accounted on the task
that sends the message, instead of the task receiving the message. This
would be bad, as you coul easily OOM a privileged task by consuming, but
never freeing its broadcasts.

Fix this by always pre-accounting the whole pool on the connection that
creates the pool.

Signed-off-by: David Herrmann <[email protected]>

pool.c

@@ -483,7 +483,7 @@ struct kdbus_pool *kdbus_pool_new(const char *name, size_t size)
 		}
 	}
 
-	f = shmem_file_setup(n ?: KBUILD_MODNAME "-conn", size, VM_NORESERVE);
+	f = shmem_file_setup(n ?: KBUILD_MODNAME "-conn", size, 0);
 	kfree(n);
 
 	if (IS_ERR(f)) {