From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Fri, 7 Sep 2018 21:55:32 +0000 (-0400)
Subject: Fix: out of memory error handling
X-Git-Tag: v2.10.8~9
X-Git-Url: http://git.liburcu.org/?p=lttng-modules.git;a=commitdiff_plain;h=fbbb0005efb47a518b8cecbaad5556c4f526074f

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 3efa1d12..7394c860 100644
--- a/lib/ringbuffer/ring_buffer_backend.c
+++ b/lib/ringbuffer/ring_buffer_backend.c
@@ -468,9 +468,11 @@ 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();