padata: add separate cpuhp node for CPUHP_PADATA_DEAD

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@oracle.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/include/linux/padata.h b/include/linux/padata.h
index a0d8b41..693cae9 100644 (file)
--- a/include/linux/padata.h
+++ b/include/linux/padata.h
@@ -139,7 +139,8 @@ struct padata_shell {
 /**
  * struct padata_instance - The overall control structure.
  *
- * @node: Used by CPU hotplug.
+ * @cpu_online_node: Linkage for CPU online callback.
+ * @cpu_dead_node: Linkage for CPU offline callback.
  * @parallel_wq: The workqueue used for parallel work.
  * @serial_wq: The workqueue used for serial work.
  * @pslist: List of padata_shell objects attached to this instance.
@@ -150,7 +151,8 @@ struct padata_shell {
  * @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         *parallel_wq;
        struct workqueue_struct         *serial_wq;
        struct list_head                pslist;

diff --git a/kernel/padata.c b/kernel/padata.c
index a6afa12..aae7898 100644 (file)
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -703,7 +703,7 @@ 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;
 
@@ -718,7 +718,7 @@ 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;
 
@@ -734,8 +734,9 @@ 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
 
        WARN_ON(!list_empty(&pinst->pslist));
@@ -939,9 +940,10 @@ static struct padata_instance *padata_alloc(const char *name,
        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
 
        put_online_cpus();