[PATCH] padata: add separate cpuhp node for CPUHP_PADATA_DEAD

[PATCH] padata: add separate cpuhp node for CPUHP_PADATA_DEAD

[Daniel Jordan]

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+
---
 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 a0d8b41850b2..693cae9bfe66 100644
--- 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 a6afa12fb75e..aae789896616 100644
--- 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();

base-commit: ae83d0b416db002fe95601e7f97f64b59514d936
-- 
2.26.0

Re: [PATCH] padata: add separate cpuhp node for CPUHP_PADATA_DEAD

[Sasha Levin]

Hi

[This is an automated email]

This commit has been processed because it contains a "Fixes:" tag
fixing commit: 894c9ef9780c ("padata: validate cpumask without removed CPU during offline").

The bot has tested the following trees: v5.6.5, v5.4.33.

v5.6.5: Build OK!
v5.4.33: Failed to apply! Possible dependencies:
    bfcdcef8c8e3 ("padata: update documentation")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

-- 
Thanks
Sasha

Re: [PATCH] padata: add separate cpuhp node for CPUHP_PADATA_DEAD

[Daniel Jordan]

On Wed, Apr 22, 2020 at 01:27:02PM +0000, Sasha Levin wrote:
> Hi

Hi!

> v5.4.33: Failed to apply! Possible dependencies:
>     bfcdcef8c8e3 ("padata: update documentation")

Yes, it's a trivial conflict in the header comment for padata_instance.

> How should we proceed with this patch?

If mainline is ok with the change, I will send a 5.4-only version with the
resolution.

By the way, I should not have cc'd stable on the email, it was picked up from
the Cc: line in the patch.

Daniel

Re: [PATCH] padata: add separate cpuhp node for CPUHP_PADATA_DEAD

[Herbert Xu]

On Tue, Apr 21, 2020 at 12:34:55PM -0400, Daniel Jordan wrote:
> 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+
> ---
>  include/linux/padata.h |  6 ++++--
>  kernel/padata.c        | 14 ++++++++------
>  2 files changed, 12 insertions(+), 8 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt