security/integrity/ima/ima_kexec.c

   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
  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_mutex is held.
  81  */
  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  */
 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 }