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

[Herbert Xu <herbert@gondor.apana.org.au>]

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/
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