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