linux-kernel - Re: [PATCH v8 4/7] ima: kexec: define functions to copy IMA log at soft boot

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Message-ID: <05eadac7-fa98-42a5-88a8-079e7c99c0b9@linux.microsoft.com>
Date: Wed, 19 Feb 2025 11:21:54 -0800
From: steven chen <chenste@...ux.microsoft.com>
To: Stefan Berger <stefanb@...ux.ibm.com>, zohar@...ux.ibm.com,
 roberto.sassu@...weicloud.com, roberto.sassu@...wei.com,
 eric.snowberg@...cle.com, ebiederm@...ssion.com, paul@...l-moore.com,
 code@...icks.com, bauermann@...abnow.com, linux-integrity@...r.kernel.org,
 kexec@...ts.infradead.org, linux-security-module@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
 James.Bottomley@...senPartnership.com, bhe@...hat.com, vgoyal@...hat.com,
 dyoung@...hat.com
Subject: Re: [PATCH v8 4/7] ima: kexec: define functions to copy IMA log at
 soft boot

On 2/19/2025 7:37 AM, Stefan Berger wrote:
>
>
> On 2/18/25 5:54 PM, steven chen wrote:
>> IMA log is copied to the new Kernel during kexec 'load' using
>
> The IMA log is currently copied to the new kernel ...
>
>
>> ima_dump_measurement_list().  The log copy at kexec 'load' may result in
>> loss of IMA measurements during kexec soft reboot.  It needs to be 
>> copied
>
> However, the log copied at kexec 'load' may result in loss of IMA 
> measurements due to missed measurements that only occurred after kexec 
> 'load'. Therefore, the log needs to be copied during kexec 'execute'. 
> Setup the ...
>
>> over during kexec 'execute'.  Setup the needed infrastructure to move 
>> the
>> IMA log copy from kexec 'load' to 'execute'.
>>
>> Define a new IMA hook ima_update_kexec_buffer() as a stub function.
>> It will be used to call ima_dump_measurement_list() during kexec
>> 'execute'.
>>
>> Implement ima_kexec_post_load() function to be invoked after the new
>> Kernel image has been loaded for kexec. ima_kexec_post_load() maps the
>> IMA buffer to a segment in the newly loaded Kernel.  It also registers
>> the reboot notifier_block to trigger ima_update_kexec_buffer() at
>> exec 'execute'.
>
> kexec 'execute'
>
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> Signed-off-by: steven chen <chenste@...ux.microsoft.com>
>
> With the above changes:
>
> Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>
>
>> ---
>>   include/linux/ima.h                |  3 ++
>>   security/integrity/ima/ima_kexec.c | 46 ++++++++++++++++++++++++++++++
>>   2 files changed, 49 insertions(+)
>>
>> diff --git a/include/linux/ima.h b/include/linux/ima.h
>> index 0bae61a15b60..8e29cb4e6a01 100644
>> --- a/include/linux/ima.h
>> +++ b/include/linux/ima.h
>> @@ -32,6 +32,9 @@ static inline void ima_appraise_parse_cmdline(void) {}
>>     #ifdef CONFIG_IMA_KEXEC
>>   extern void ima_add_kexec_buffer(struct kimage *image);
>> +extern void ima_kexec_post_load(struct kimage *image);
>> +#else
>> +static inline void ima_kexec_post_load(struct kimage *image) {}
>>   #endif
>>     #else
>> diff --git a/security/integrity/ima/ima_kexec.c 
>> b/security/integrity/ima/ima_kexec.c
>> index 704676fa6615..0fa65f91414b 100644
>> --- a/security/integrity/ima/ima_kexec.c
>> +++ b/security/integrity/ima/ima_kexec.c
>> @@ -12,10 +12,14 @@
>>   #include <linux/kexec.h>
>>   #include <linux/of.h>
>>   #include <linux/ima.h>
>> +#include <linux/reboot.h>
>> +#include <asm/page.h>
>>   #include "ima.h"
>>     #ifdef CONFIG_IMA_KEXEC
>>   static struct seq_file ima_kexec_file;
>> +static void *ima_kexec_buffer;
>> +static bool ima_kexec_update_registered;
>>     static void ima_reset_kexec_file(struct seq_file *sf)
>>   {
>> @@ -183,6 +187,48 @@ void ima_add_kexec_buffer(struct kimage *image)
>>       kexec_dprintk("kexec measurement buffer for the loaded kernel 
>> at 0x%lx.\n",
>>                 kbuf.mem);
>>   }
>> +
>> +/*
>> + * Called during kexec execute so that IMA can update the 
>> measurement list.
>> + */
>> +static int ima_update_kexec_buffer(struct notifier_block *self,
>> +                   unsigned long action, void *data)
>> +{
>> +    return NOTIFY_OK;
>> +}
>> +
>> +struct notifier_block update_buffer_nb = {
>> +    .notifier_call = ima_update_kexec_buffer,
>> +};
>> +
>> +/*
>> + * Create a mapping for the source pages that contain the IMA buffer
>> + * so we can update it later.
>> + */
>> +void ima_kexec_post_load(struct kimage *image)
>> +{
>> +    if (ima_kexec_buffer) {
>> +        kimage_unmap_segment(ima_kexec_buffer);
>> +        ima_kexec_buffer = NULL;
>> +    }
>> +
>> +    if (!image->ima_buffer_addr)
>> +        return;
>> +
>> +    ima_kexec_buffer = kimage_map_segment(image,
>> +                          image->ima_buffer_addr,
>> +                          image->ima_buffer_size);
>> +    if (!ima_kexec_buffer) {
>> +        pr_err("Could not map measurements buffer.\n");
>> +        return;
>> +    }
>> +
>> +    if (!ima_kexec_update_registered) {
>> +        register_reboot_notifier(&update_buffer_nb);
>> +        ima_kexec_update_registered = true;
>> +    }
>> +}
>> +
>>   #endif /* IMA_KEXEC */
>>     /*

Hi Stefan, thanks for your comments. I will update in next version.