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Message-ID: <7433b986-f048-494d-a66a-5888cd37b081@linux.ibm.com>
Date: Wed, 19 Feb 2025 10:57:13 -0500
From: Stefan Berger <stefanb@...ux.ibm.com>
To: steven chen <chenste@...ux.microsoft.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 2/18/25 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 = {
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