Re: [PATCH] crash_dump: Fix potential double free and UAF of keys_header

[Coiby Xu]

On Tue, Apr 07, 2026 at 03:29:18PM +0530, Sourabh Jain wrote:
>
[...]
> > > As per kdump.rst, restore was introduced to handle CPU and
> > > memory hotplug cases. Is it needed when there is no in-kernel
> > > update to the kdump image on CPU or memory hotplug events?
> > >
> > > But in that case, we rely on a udev rule to reload the kdump image
> > > again.
> > >
> > > I am confused about when exactly we need to restore.
> >
> > To clarify, reuse other than restore is needed for non in-kernel update
> > when handing CPU/memory hotplugging. Yes, a udev rule is also needed in
> > this case.
>
> Below commit explains how the reuse is utilized:
>
> commit 9ebfa8dcaea77a8ef02d0f9478717a138b0ad828
> Author: Coiby Xu <coxu@xxxxxxxxxx>
> Date:   Fri May 2 09:12:38 2025 +0800
>
>     crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging
>
> It got it now. This is helpful when kdump needs to be reloaded due to
> CPU/memory hotplug events using the kexec_file_load system call,
> but only when CONFIG_CRASH_HOTPLUG is not enabled.


> IIUC this feature is not support on crash image loaded using 
> kexec_load syscall, right?

Glad you've figured it out!  Yes, you are correct. If
CONFIG_CRASH_HOTPLUG is enabled, there is no need for configfs/reuse. In
v2, I've improved the doc and also added a patch to prevented using this
API when CONFIG_CRASH_HOTPLUG is enabled.


--
Best regards,
Coiby