Re: [PATCH v5 5/8] ima: kexec: move IMA log copy from kexec load to execute

From: "Petr Tesařík" <petr@tesarici.cz>
To: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Cc: zohar@linux.ibm.com, roberto.sassu@huaweicloud.com,
	roberto.sassu@huawei.com, eric.snowberg@oracle.com,
	stefanb@linux.ibm.com, ebiederm@xmission.com, noodles@fb.com,
	bauermann@kolabnow.com, linux-integrity@vger.kernel.org,
	kexec@lists.infradead.org, code@tyhicks.com,
	nramas@linux.microsoft.com, paul@paul-moore.com
Subject: Re: [PATCH v5 5/8] ima: kexec: move IMA log copy from kexec load to execute
Date: Thu, 9 May 2024 08:32:05 +0200	[thread overview]
Message-ID: <20240509083205.17d53ccb@meshulam.tesarici.cz> (raw)
In-Reply-To: <20240214153827.1087657-6-tusharsu@linux.microsoft.com>

On Wed, 14 Feb 2024 07:38:24 -0800
Tushar Sugandhi <tusharsu@linux.microsoft.com> wrote:

> ima_dump_measurement_list() is called during kexec 'load', which may
> result in loss of IMA measurements during kexec soft reboot.  It needs
> to be called during kexec 'execute'.
> 
> This patch includes the following changes:
>  - 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
>    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.
> 
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> ---
>  kernel/kexec_file.c                |  3 ++
>  security/integrity/ima/ima_kexec.c | 45 +++++++++++++++++++-----------
>  2 files changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index fe59cb7c179d..2d5df320c34f 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -410,6 +410,9 @@ 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 1d4d6c122d82..98fc9b9782a2 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;
> -	size_t kexec_segment_size;
>  	int ret;
>  
>  	/*
> @@ -154,14 +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("%s: Failed to dump IMA measurements. Error:%d.\n",
> -		       __func__, ret);
> -		return;
> -	}
> -

After removing these lines...

>  	kbuf.buffer = kexec_buffer;
>  	kbuf.bufsz = kexec_buffer_size;
                     ^^^^^^^^^^^^^^^^^

... kexec_buffer_size is uninitialized here.

Petr T