[PATCH 4.19 2/2] padata: add separate cpuhp node for CPUHP_PADATA_DEAD

[Yang Yingliang]

From: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>

[ Upstream commit 3c2214b6027ff37945799de717c417212e1a8c54 ]

Removing the pcrypt module triggers this:

  general protection fault, probably for non-canonical
    address 0xdead000000000122
  CPU: 5 PID: 264 Comm: modprobe Not tainted 5.6.0+ #2
  Hardware name: QEMU Standard PC
  RIP: 0010:__cpuhp_state_remove_instance+0xcc/0x120
  Call Trace:
   padata_sysfs_release+0x74/0xce
   kobject_put+0x81/0xd0
   padata_free+0x12/0x20
   pcrypt_exit+0x43/0x8ee [pcrypt]

padata instances wrongly use the same hlist node for the online and dead
states, so __padata_free()'s second cpuhp remove call chokes on the node
that the first poisoned.

cpuhp multi-instance callbacks only walk forward in cpuhp_step->list and
the same node is linked in both the online and dead lists, so the list
corruption that results from padata_alloc() adding the node to a second
list without removing it from the first doesn't cause problems as long
as no instances are freed.

Avoid the issue by giving each state its own node.

Fixes: 894c9ef9780c ("padata: validate cpumask without removed CPU during offline")
Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Cc: linux-crypto@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # v5.4+
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
---
 include/linux/padata.h |  6 ++++--
 kernel/padata.c        | 14 ++++++++------
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/linux/padata.h b/include/linux/padata.h
index d803397a28f70..8c9827cc63747 100644
--- a/include/linux/padata.h
+++ b/include/linux/padata.h
@@ -138,7 +138,8 @@ struct parallel_data {
 /**
  * struct padata_instance - The overall control structure.
  *
- * @cpu_notifier: cpu hotplug notifier.
+ * @cpu_online_node: Linkage for CPU online callback.
+ * @cpu_dead_node: Linkage for CPU offline callback.
  * @wq: The workqueue in use.
  * @pd: The internal control structure.
  * @cpumask: User supplied cpumasks for parallel and serial works.
@@ -150,7 +151,8 @@ struct parallel_data {
  * @flags: padata flags.
  */
 struct padata_instance {
-	struct hlist_node		 node;
+	struct hlist_node		cpu_online_node;
+	struct hlist_node		cpu_dead_node;
 	struct workqueue_struct		*wq;
 	struct parallel_data		*pd;
 	struct padata_cpumask		cpumask;
diff --git a/kernel/padata.c b/kernel/padata.c
index 4401b4f13d0be..7f2b6d369fd47 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -748,7 +748,7 @@ static int padata_cpu_online(unsigned int cpu, struct hlist_node *node)
 	struct padata_instance *pinst;
 	int ret;
 
-	pinst = hlist_entry_safe(node, struct padata_instance, node);
+	pinst = hlist_entry_safe(node, struct padata_instance, cpu_online_node);
 	if (!pinst_has_cpu(pinst, cpu))
 		return 0;
 
@@ -763,7 +763,7 @@ static int padata_cpu_dead(unsigned int cpu, struct hlist_node *node)
 	struct padata_instance *pinst;
 	int ret;
 
-	pinst = hlist_entry_safe(node, struct padata_instance, node);
+	pinst = hlist_entry_safe(node, struct padata_instance, cpu_dead_node);
 	if (!pinst_has_cpu(pinst, cpu))
 		return 0;
 
@@ -779,8 +779,9 @@ static enum cpuhp_state hp_online;
 static void __padata_free(struct padata_instance *pinst)
 {
 #ifdef CONFIG_HOTPLUG_CPU
-	cpuhp_state_remove_instance_nocalls(CPUHP_PADATA_DEAD, &pinst->node);
-	cpuhp_state_remove_instance_nocalls(hp_online, &pinst->node);
+	cpuhp_state_remove_instance_nocalls(CPUHP_PADATA_DEAD,
+					    &pinst->cpu_dead_node);
+	cpuhp_state_remove_instance_nocalls(hp_online, &pinst->cpu_online_node);
 #endif
 
 	padata_stop(pinst);
@@ -964,9 +965,10 @@ static struct padata_instance *padata_alloc(struct workqueue_struct *wq,
 	mutex_init(&pinst->lock);
 
 #ifdef CONFIG_HOTPLUG_CPU
-	cpuhp_state_add_instance_nocalls_cpuslocked(hp_online, &pinst->node);
+	cpuhp_state_add_instance_nocalls_cpuslocked(hp_online,
+						    &pinst->cpu_online_node);
 	cpuhp_state_add_instance_nocalls_cpuslocked(CPUHP_PADATA_DEAD,
-						    &pinst->node);
+						    &pinst->cpu_dead_node);
 #endif
 	return pinst;
 
-- 
2.25.1