security/integrity/ima/ima_kexec.c

   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 }