linux-kernel - Re: [PATCH v7 2/7] crash_dump: make dm crypt keys persist for the kdump kernel

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Message-ID: <4a663a07-2442-4552-b524-a5cc6b06b727@infradead.org>
Date: Wed, 15 Jan 2025 23:04:23 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Coiby Xu <coxu@...hat.com>, kexec@...ts.infradead.org
Cc: Ondrej Kozina <okozina@...hat.com>, Milan Broz <gmazyland@...il.com>,
 Thomas Staudt <tstaudt@...ibm.com>, Daniel P . Berrangé
 <berrange@...hat.com>, Kairui Song <ryncsn@...il.com>,
 Jan Pazdziora <jpazdziora@...hat.com>, Pingfan Liu <kernelfans@...il.com>,
 Baoquan He <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
 linux-kernel@...r.kernel.org, x86@...nel.org,
 Dave Hansen <dave.hansen@...el.com>, Vitaly Kuznetsov <vkuznets@...hat.com>,
 Vivek Goyal <vgoyal@...hat.com>, Jonathan Corbet <corbet@....net>,
 "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v7 2/7] crash_dump: make dm crypt keys persist for the
 kdump kernel

Hi,

On 1/15/25 10:58 PM, Coiby Xu wrote:
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index 5376890adbeb..192d6796ab94 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -551,6 +551,34 @@ from within add_taint() whenever the value set in this bitmask matches with the
>  bit flag being set by add_taint().
>  This will cause a kdump to occur at the add_taint()->panic() call.
>  
> +Write the dump file to encrypted disk volume
> +============================================
> +
> +CONFIG_CRASH_DM_CRYPT can be enabled to support saving the dump file to
> +encrypted disk volume. User space can interact with

   an encrypted disk volume.

> +/sys/kernel/config/crash_dm_crypt_keys for setup,
> +
> +1. Tell the 1st kernel what keys are needed to unlock the disk volumes,

               first

> +    # Add key #1
> +    mkdir /sys/kernel/config/crash_dm_crypt_keys/7d26b7b4-e342-4d2d-b660-7426b0996720
> +    # Add key #1's description
> +    echo cryptsetup:7d26b7b4-e342-4d2d-b660-7426b0996720 > /sys/kernel/config/crash_dm_crypt_keys/description
> +
> +    # how many keys do we have now?
> +    cat /sys/kernel/config/crash_dm_crypt_keys/count
> +    1
> +
> +    # Add key#2 in the same way

             key #2
(be consisent)

> +
> +    # how many keys do we have now?
> +    cat /sys/kernel/config/crash_dm_crypt_keys/count
> +    2
> +
> +2. Load the dump-capture kernel
> +
> +3. After dump-capture kerne get booted, restore the keys to user keyring

      After the dump-capture kernel is booted,

> +   echo yes > /sys/kernel/crash_dm_crypt_keys/restore
> +
>  Contact
>  =======
>  

-- 
~Randy