Fix: out of memory error handling

CPU hotplug handles teardown on failure to complete adding an instance
of CPU hotplug. Trying to remove after a failed "add" on that instance
triggers a NULL pointer dereference OOPS.

Fixes: #1167
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/lib/ringbuffer/ring_buffer_backend.c b/lib/ringbuffer/ring_buffer_backend.c
index 54c62a996764ee2ee004ee96f3a188801ae6d871..9d199e516aacbaf009538faf394671113e18bf70 100644 (file)
--- a/lib/ringbuffer/ring_buffer_backend.c
+++ b/lib/ringbuffer/ring_buffer_backend.c
@@ -455,9 +455,11 @@ int channel_backend_init(struct channel_backend *chanb,
 free_bufs:
        if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0))
-               ret = cpuhp_state_remove_instance(lttng_rb_hp_prepare,
-                               &chanb->cpuhp_prepare.node);
-               WARN_ON(ret);
+               /*
+                * Teardown of lttng_rb_hp_prepare instance
+                * on "add" error is handled within cpu hotplug,
+                * no teardown to do from the caller.
+                */
 #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)) */
 #ifdef CONFIG_HOTPLUG_CPU
                put_online_cpus();