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[v4,3/7] ima: kexec: skip IMA segment validation after kexec soft reboot

Message ID 20240122183804.3293904-4-tusharsu@linux.microsoft.com (mailing list archive)
State New, archived
Headers show
Series ima: kexec: measure events between kexec load and execute | expand

Commit Message

Tushar Sugandhi Jan. 22, 2024, 6:38 p.m. UTC 
kexec_calculate_store_digests() calculates and stores the digest of the
segment at kexec_file_load syscall where the IMA segment is also
allocated.  With this series, the IMA segment will be updated with the
measurement log at kexec soft reboot.  Therefore, it may fail digest
verification in verify_sha256_digest() after kexec soft reboot into the
new Kernel.

Skip IMA segment from calculating and storing digest in function
kexec_calculate_store_digests() so that it is not added to the
'purgatory_sha_regions'.

Since verify_sha256_digest() only verifies 'purgatory_sha_regions',
no change is needed in verify_sha256_digest() in this context.

With this change, the IMA segment is not included in the digest
calculation, storage, and verification.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 include/linux/kexec.h              | 3 +++
 kernel/kexec_file.c                | 8 ++++++++
 security/integrity/ima/ima_kexec.c | 3 +++
 3 files changed, 14 insertions(+)
diff mbox series

Patch

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index e00b8101b53b..eb98aca7f4c7 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -366,6 +366,9 @@  struct kimage {
 
 	phys_addr_t ima_buffer_addr;
 	size_t ima_buffer_size;
+
+	unsigned long ima_segment_index;
+	bool is_ima_segment_index_set;
 #endif
 
 	/* Core ELF header buffer */
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f989f5f1933b..bf758fd5062c 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -734,6 +734,14 @@  static int kexec_calculate_store_digests(struct kimage *image)
 		if (ksegment->kbuf == pi->purgatory_buf)
 			continue;
 
+		/*
+		 * Skip the segment if ima_segment_index is set and matches
+		 * the current index
+		 */
+		if (image->is_ima_segment_index_set &&
+		    i == image->ima_segment_index)
+			continue;
+
 		ret = crypto_shash_update(desc, ksegment->kbuf,
 					  ksegment->bufsz);
 		if (ret)
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 4f944c9b4168..d92a48284cc4 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -156,6 +156,7 @@  void ima_add_kexec_buffer(struct kimage *image)
 	kbuf.buffer = kexec_buffer;
 	kbuf.bufsz = kexec_buffer_size;
 	kbuf.memsz = kexec_segment_size;
+	image->is_ima_segment_index_set = false;
 	ret = kexec_add_buffer(&kbuf);
 	if (ret) {
 		pr_err("Error passing over kexec measurement buffer.\n");
@@ -166,6 +167,8 @@  void ima_add_kexec_buffer(struct kimage *image)
 	image->ima_buffer_addr = kbuf.mem;
 	image->ima_buffer_size = kexec_segment_size;
 	image->ima_buffer = kexec_buffer;
+	image->ima_segment_index = image->nr_segments - 1;
+	image->is_ima_segment_index_set = true;
 
 	pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
 		 kbuf.mem);