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