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Message-ID: <53a254d2-3aec-4bfa-9eca-e17f22e47b5c@linux.microsoft.com>
Date: Wed, 19 Feb 2025 11:23:29 -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 5/7] ima: kexec: move IMA log copy from kexec load to
execute
On 2/19/2025 7:57 AM, Stefan Berger wrote:
>
>
> On 2/18/25 5:55 PM, steven chen wrote:
>> ima_dump_measurement_list() is called during kexec 'load', which may
>> result in loss of IMA measurements during kexec soft reboot. It needs
>
> ... due to missed measurements that only occurred after kexec 'load'.
> Therefore, this function needs to be ...
>
>> to be called during kexec 'execute'.
>>
>> This patch includes the following changes:
>> - Implement kimage_file_post_load() function to be invoked after
>> the new
>> Kernel image has been loaded for kexec.
>
> s/Kernel/kernel
>
>> - Call kimage_file_post_load() from kexec_file_load() syscall only for
>> kexec soft reboot scenarios and not for KEXEC_FILE_ON_CRASH. It
>> will
>> map the IMA segment, and register reboot notifier for the function
>> ima_update_kexec_buffer() which would copy the IMA log at kexec soft
>> reboot.
>> - Make kexec_segment_size variable local static to the file, for it
>> to be
>
> ... to the file so that it becomes accessible ...
>
>> accessible both during kexec 'load' and 'execute'.
>> - Move ima_dump_measurement_list() call from ima_add_kexec_buffer()
>> to ima_update_kexec_buffer().
>> - Remove ima_reset_kexec_file() call from ima_add_kexec_buffer(), now
>> that the buffer is being copied at kexec 'execute', and resetting
>> the
>> file at kexec 'load' will corrupt the buffer.
>
> s/will/would
>
>>
>> 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>
>
>> ---
>> kernel/kexec_file.c | 8 ++++++
>> security/integrity/ima/ima_kexec.c | 43 +++++++++++++++++++-----------
>> 2 files changed, 36 insertions(+), 15 deletions(-)
>>
>> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
>> index 606132253c79..76b6a877b842 100644
>> --- a/kernel/kexec_file.c
>> +++ b/kernel/kexec_file.c
>> @@ -201,6 +201,11 @@ kimage_validate_signature(struct kimage *image)
>> }
>> #endif
>> +static void kimage_file_post_load(struct kimage *image)
>> +{
>> + ima_kexec_post_load(image);
>> +}
>> +
>> /*
>> * In file mode list of segments is prepared by kernel. Copy relevant
>> * data from user space, do error checking, prepare segment list
>> @@ -428,6 +433,9 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd,
>> int, initrd_fd,
>> kimage_terminate(image);
>> + if (!(flags & KEXEC_FILE_ON_CRASH))
>> + kimage_file_post_load(image);
>> +
>> ret = machine_kexec_post_load(image);
>> if (ret)
>> goto out;
>> diff --git a/security/integrity/ima/ima_kexec.c
>> b/security/integrity/ima/ima_kexec.c
>> index 0fa65f91414b..f9dd7ff95b84 100644
>> --- a/security/integrity/ima/ima_kexec.c
>> +++ b/security/integrity/ima/ima_kexec.c
>> @@ -19,6 +19,7 @@
>> #ifdef CONFIG_IMA_KEXEC
>> static struct seq_file ima_kexec_file;
>> static void *ima_kexec_buffer;
>> +static size_t kexec_segment_size;
>> static bool ima_kexec_update_registered;
>> static void ima_reset_kexec_file(struct seq_file *sf)
>> @@ -129,7 +130,6 @@ void ima_add_kexec_buffer(struct kimage *image)
>> /* use more understandable variable names than defined in kbuf */
>> void *kexec_buffer = NULL;
>> size_t kexec_buffer_size = 0;
>> - size_t kexec_segment_size;
>> int ret;
>> /*
>> @@ -154,13 +154,6 @@ void ima_add_kexec_buffer(struct kimage *image)
>> return;
>> }
>> - ret = ima_dump_measurement_list(&kexec_buffer_size,
>> &kexec_buffer,
>> - kexec_segment_size);
>> - if (ret < 0) {
>> - pr_err("Failed to dump IMA measurements. Error:%d.\n", ret);
>> - return;
>> - }
>> -
>> kbuf.buffer = kexec_buffer;
>> kbuf.bufsz = kexec_buffer_size;
>> kbuf.memsz = kexec_segment_size;
>> @@ -178,12 +171,6 @@ void ima_add_kexec_buffer(struct kimage *image)
>> image->ima_segment_index = image->nr_segments - 1;
>> image->is_ima_segment_index_set = true;
>> - /*
>> - * kexec owns kexec_buffer after kexec_add_buffer() is called
>> - * and it will vfree() that buffer.
>> - */
>> - ima_reset_kexec_file(&ima_kexec_file);
>> -
>> kexec_dprintk("kexec measurement buffer for the loaded kernel
>> at 0x%lx.\n",
>> kbuf.mem);
>> }
>> @@ -194,7 +181,33 @@ void ima_add_kexec_buffer(struct kimage *image)
>> static int ima_update_kexec_buffer(struct notifier_block *self,
>> unsigned long action, void *data)
>> {
>> - return NOTIFY_OK;
>> + void *buf = NULL;
>> + size_t buf_size = 0;
>> + int ret = NOTIFY_OK;
>> +
>> + if (!kexec_in_progress) {
>> + pr_info("No kexec in progress.\n");
>> + return ret;
>> + }
>> +
>> + if (!ima_kexec_buffer) {
>> + pr_err("Kexec buffer not set.\n");
>> + return ret;
>> + }
>> +
>> + ret = ima_dump_measurement_list(&buf_size, &buf,
>> + kexec_segment_size);
>> +
>> + if (ret)
>> + pr_err("Dump measurements failed. Error:%d\n", ret);
>> +
>> + if (buf_size != 0)
>> + memcpy(ima_kexec_buffer, buf, buf_size);
>> +
>> + kimage_unmap_segment(ima_kexec_buffer);
>> + ima_kexec_buffer = NULL;
>> +
>> + return ret;
>> }
>> struct notifier_block update_buffer_nb = {
Hi Stefan, thanks for your comments. I will update in next version.
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