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