1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2016 IBM Corporation
4 *
5 * Authors:
6 * Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
7 * Mimi Zohar <zohar@linux.vnet.ibm.com>
8 */
9
10#include <linux/seq_file.h>
11#include <linux/vmalloc.h>
12#include <linux/kexec.h>
13#include <linux/ima.h>
14#include "ima.h"
15
16#ifdef CONFIG_IMA_KEXEC
17static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
18				     unsigned long segment_size)
19{
20	struct ima_queue_entry *qe;
21	struct seq_file file;
22	struct ima_kexec_hdr khdr;
23	int ret = 0;
24
25	/* segment size can't change between kexec load and execute */
26	file.buf = vmalloc(segment_size);
27	if (!file.buf) {
28		ret = -ENOMEM;
29		goto out;
30	}
31
32	file.size = segment_size;
33	file.read_pos = 0;
34	file.count = sizeof(khdr);	/* reserved space */
35
36	memset(&khdr, 0, sizeof(khdr));
37	khdr.version = 1;
38	list_for_each_entry_rcu(qe, &ima_measurements, later) {
39		if (file.count < file.size) {
40			khdr.count++;
41			ima_measurements_show(&file, qe);
42		} else {
43			ret = -EINVAL;
44			break;
45		}
46	}
47
48	if (ret < 0)
49		goto out;
50
51	/*
52	 * fill in reserved space with some buffer details
53	 * (eg. version, buffer size, number of measurements)
54	 */
55	khdr.buffer_size = file.count;
56	if (ima_canonical_fmt) {
57		khdr.version = cpu_to_le16(khdr.version);
58		khdr.count = cpu_to_le64(khdr.count);
59		khdr.buffer_size = cpu_to_le64(khdr.buffer_size);
60	}
61	memcpy(file.buf, &khdr, sizeof(khdr));
62
63	print_hex_dump(KERN_DEBUG, "ima dump: ", DUMP_PREFIX_NONE,
64			16, 1, file.buf,
65			file.count < 100 ? file.count : 100, true);
66
67	*buffer_size = file.count;
68	*buffer = file.buf;
69out:
70	if (ret == -EINVAL)
71		vfree(file.buf);
72	return ret;
73}
74
75/*
76 * Called during kexec_file_load so that IMA can add a segment to the kexec
77 * image for the measurement list for the next kernel.
78 *
79 * This function assumes that kexec_mutex is held.
80 */
81void ima_add_kexec_buffer(struct kimage *image)
82{
83	struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
84				  .buf_min = 0, .buf_max = ULONG_MAX,
85				  .top_down = true };
86	unsigned long binary_runtime_size;
87
88	/* use more understandable variable names than defined in kbuf */
89	void *kexec_buffer = NULL;
90	size_t kexec_buffer_size;
91	size_t kexec_segment_size;
92	int ret;
93
94	/*
95	 * Reserve an extra half page of memory for additional measurements
96	 * added during the kexec load.
97	 */
98	binary_runtime_size = ima_get_binary_runtime_size();
99	if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE)
100		kexec_segment_size = ULONG_MAX;
101	else
102		kexec_segment_size = ALIGN(ima_get_binary_runtime_size() +
103					   PAGE_SIZE / 2, PAGE_SIZE);
104	if ((kexec_segment_size == ULONG_MAX) ||
105	    ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) {
106		pr_err("Binary measurement list too large.\n");
107		return;
108	}
109
110	ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
111				  kexec_segment_size);
112	if (!kexec_buffer) {
113		pr_err("Not enough memory for the kexec measurement buffer.\n");
114		return;
115	}
116
117	kbuf.buffer = kexec_buffer;
118	kbuf.bufsz = kexec_buffer_size;
119	kbuf.memsz = kexec_segment_size;
120	ret = kexec_add_buffer(&kbuf);
121	if (ret) {
122		pr_err("Error passing over kexec measurement buffer.\n");
123		vfree(kexec_buffer);
124		return;
125	}
126
127	ret = arch_ima_add_kexec_buffer(image, kbuf.mem, kexec_segment_size);
128	if (ret) {
129		pr_err("Error passing over kexec measurement buffer.\n");
130		return;
131	}
132
133	image->ima_buffer = kexec_buffer;
134
135	pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
136		 kbuf.mem);
137}
138#endif /* IMA_KEXEC */
139
140/*
141 * Restore the measurement list from the previous kernel.
142 */
143void ima_load_kexec_buffer(void)
144{
145	void *kexec_buffer = NULL;
146	size_t kexec_buffer_size = 0;
147	int rc;
148
149	rc = ima_get_kexec_buffer(&kexec_buffer, &kexec_buffer_size);
150	switch (rc) {
151	case 0:
152		rc = ima_restore_measurement_list(kexec_buffer_size,
153						  kexec_buffer);
154		if (rc != 0)
155			pr_err("Failed to restore the measurement list: %d\n",
156				rc);
157
158		ima_free_kexec_buffer();
159		break;
160	case -ENOTSUPP:
161		pr_debug("Restoring the measurement list not supported\n");
162		break;
163	case -ENOENT:
164		pr_debug("No measurement list to restore\n");
165		break;
166	default:
167		pr_debug("Error restoring the measurement list: %d\n", rc);
168	}
169}
170