linux-kernel - Re: [PATCH v7 1/7] ima: define and call ima_alloc_kexec_file

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Message-ID: <ba702678-e1a3-49b5-9c5e-76329e83c812@linux.microsoft.com>
Date: Fri, 7 Feb 2025 11:23:40 -0800
From: steven chen <chenste@...ux.microsoft.com>
To: Mimi Zohar <zohar@...ux.ibm.com>, stefanb@...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
Subject: Re: [PATCH v7 1/7] ima: define and call ima_alloc_kexec_file_buf

On 2/7/2025 11:10 AM, Mimi Zohar wrote:
> On Mon, 2025-02-03 at 15:20 -0800, steven chen wrote:
>> Carrying the IMA measurement list across kexec requires allocating a
>> buffer and copying the measurement records.  Separate allocating the
>> buffer and copying the measurement records into separate functions in
>> order to allocate the buffer at kexec 'load' and copy the measurements
>> at kexec 'execute'.
>>
>> This patch includes the following changes:
>>   - Refactor ima_dump_measurement_list() to move the memory allocation
>>     to a separate function ima_alloc_kexec_file_buf() which allocates
>>     buffer of size 'kexec_segment_size' at kexec 'load'.
>>   - Make the local variable ima_kexec_file in ima_dump_measurement_list()
>>     a local static to the file, so that it can be accessed from
>>     ima_alloc_kexec_file_buf(). Compare actual memory required to ensure
>>     there is enough memory for the entire measurement record.
>>   - Copy as many measurement events as possible.
>>   - Make necessary changes to the function ima_add_kexec_buffer() to call
>>     the above two functions.
>>   - Compared the memory size allocated with memory size of the entire
>>     measurement record. If there is not enough memory, it will copy as many
>>     IMA measurement records as possible, and this situation will result
>>     in a failure of remote attestation.
>>
>> Author: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>
>> Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
>> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> Signed-off-by: steven chen <chenste@...ux.microsoft.com>
>> ---
>>   security/integrity/ima/ima.h       |   1 +
>>   security/integrity/ima/ima_kexec.c | 105 +++++++++++++++++++++--------
>>   security/integrity/ima/ima_queue.c |   4 +-
>>   3 files changed, 80 insertions(+), 30 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
>> index 3c323ca213d4..447a6eb07c2d 100644
>> --- a/security/integrity/ima/ima.h
>> +++ b/security/integrity/ima/ima.h
>> @@ -274,6 +274,7 @@ bool ima_template_has_modsig(const struct ima_template_desc
>> *ima_template);
>>   int ima_restore_measurement_entry(struct ima_template_entry *entry);
>>   int ima_restore_measurement_list(loff_t bufsize, void *buf);
>>   int ima_measurements_show(struct seq_file *m, void *v);
>> +int ima_get_binary_runtime_entry_size(struct ima_template_entry *entry);
>>   unsigned long ima_get_binary_runtime_size(void);
>>   int ima_init_template(void);
>>   void ima_init_template_list(void);
>> diff --git a/security/integrity/ima/ima_kexec.c
>> b/security/integrity/ima/ima_kexec.c
>> index 52e00332defe..b60a902460e2 100644
>> --- a/security/integrity/ima/ima_kexec.c
>> +++ b/security/integrity/ima/ima_kexec.c
>> @@ -15,62 +15,99 @@
>>   #include "ima.h"
>>   
>>   #ifdef CONFIG_IMA_KEXEC
>> +static struct seq_file ima_kexec_file;
>> +
>> +static void ima_reset_kexec_file(struct seq_file *sf)
>> +{
>> +	sf->buf = NULL;
>> +	sf->size = 0;
>> +	sf->read_pos = 0;
>> +	sf->count = 0;
>> +}
>> +
>> +static void ima_free_kexec_file_buf(struct seq_file *sf)
>> +{
>> +	vfree(sf->buf);
>> +	ima_reset_kexec_file(sf);
>> +}
>> +
>> +static int ima_alloc_kexec_file_buf(size_t segment_size)
>> +{
>> +	/*
>> +	 * kexec 'load' may be called multiple times.
>> +	 * Free and realloc the buffer only if the segment_size is
>> +	 * changed from the previous kexec 'load' call.
>> +	 */
>> +	if (ima_kexec_file.buf &&
>> +		(ima_kexec_file.size == segment_size)) {
>> +		goto out;
>> +	}
> Nice cleanup from v5.  The line doesn't doesn't need to be split.  Both the
> parenthesis and the brackets can be removed.
>
> In the future, before posting patches, please use scripts/checkpatch.pl.
>
> CHECK: Unnecessary parentheses around 'ima_kexec_file.size == segment_size'
> #82: FILE: security/integrity/ima/ima_kexec.c:41:
> +	if (ima_kexec_file.buf &&
> +		(ima_kexec_file.size == segment_size)) {
>
> CHECK: Alignment should match open parenthesis
> #83: FILE: security/integrity/ima/ima_kexec.c:42:
> +	if (ima_kexec_file.buf &&
> +		(ima_kexec_file.size == segment_size)) {
>
> Or simply join the two lines.
>
> thanks,
>
> Mimi
>
>> +
>> +	ima_free_kexec_file_buf(&ima_kexec_file);
>> +
>> +	/* segment size can't change between kexec load and execute */
>> +	ima_kexec_file.buf = vmalloc(segment_size);
>> +	if (!ima_kexec_file.buf)
>> +		return -ENOMEM;
>> +
>> +	ima_kexec_file.size = segment_size;
>> +
>> +out:
>> +	ima_kexec_file.read_pos = 0;
>> +	ima_kexec_file.count = sizeof(struct ima_kexec_hdr);	/* reserved space
>> */
>> +
>> +	return 0;
>> +}
>>
Thanks, Mimi, will update in the next release