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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10
  11 #include <linux/seq_file.h>
  12 #include <linux/vmalloc.h>
  13 #include <linux/kexec.h>
  14 #include "ima.h"
  15
  16 #ifdef CONFIG_IMA_KEXEC
  17 static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
  18                                      unsigned long segment_size)
  19 {
  20         struct ima_queue_entry *qe;
  21         struct seq_file file;
  22         struct ima_kexec_hdr khdr;
  23         int ret = 0;
  24
  25         /* segment size can't change between kexec load and execute */
  26         file.buf = vmalloc(segment_size);
  27         if (!file.buf) {
  28                 ret = -ENOMEM;
  29                 goto out;
  30         }
  31
  32         file.size = segment_size;
  33         file.read_pos = 0;
  34         file.count = sizeof(khdr);      /* reserved space */
  35
  36         memset(&khdr, 0, sizeof(khdr));
  37         khdr.version = 1;
  38         list_for_each_entry_rcu(qe, &ima_measurements, later) {
  39                 if (file.count < file.size) {
  40                         khdr.count++;
  41                         ima_measurements_show(&file, qe);
  42                 } else {
  43                         ret = -EINVAL;
  44                         break;
  45                 }
  46         }
  47
  48         if (ret < 0)
  49                 goto out;
  50
  51         /*
  52          * fill in reserved space with some buffer details
  53          * (eg. version, buffer size, number of measurements)
  54          */
  55         khdr.buffer_size = file.count;
  56         if (ima_canonical_fmt) {
  57                 khdr.version = cpu_to_le16(khdr.version);
  58                 khdr.count = cpu_to_le64(khdr.count);
  59                 khdr.buffer_size = cpu_to_le64(khdr.buffer_size);
  60         }
  61         memcpy(file.buf, &khdr, sizeof(khdr));
  62
  63         print_hex_dump(KERN_DEBUG, "ima dump: ", DUMP_PREFIX_NONE,
  64                         16, 1, file.buf,
  65                         file.count < 100 ? file.count : 100, true);
  66
  67         *buffer_size = file.count;
  68         *buffer = file.buf;
  69 out:
  70         if (ret == -EINVAL)
  71                 vfree(file.buf);
  72         return ret;
  73 }
  74
  75 /*
  76  * Called during kexec_file_load so that IMA can add a segment to the kexec
  77  * image for the measurement list for the next kernel.
  78  *
  79  * This function assumes that kexec_mutex is held.
  80  */
  81 void ima_add_kexec_buffer(struct kimage *image)
  82 {
  83         struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
  84                                   .buf_min = 0, .buf_max = ULONG_MAX,
  85                                   .top_down = true };
  86         unsigned long binary_runtime_size;
  87
  88         /* use more understandable variable names than defined in kbuf */
  89         void *kexec_buffer = NULL;
  90         size_t kexec_buffer_size;
  91         size_t kexec_segment_size;
  92         int ret;
  93
  94         /*
  95          * Reserve an extra half page of memory for additional measurements
  96          * added during the kexec load.
  97          */
  98         binary_runtime_size = ima_get_binary_runtime_size();
  99         if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE)
 100                 kexec_segment_size = ULONG_MAX;
 101         else
 102                 kexec_segment_size = ALIGN(ima_get_binary_runtime_size() +
 103                                            PAGE_SIZE / 2, PAGE_SIZE);
 104         if ((kexec_segment_size == ULONG_MAX) ||
 105             ((kexec_segment_size >> PAGE_SHIFT) > totalram_pages() / 2)) {
 106                 pr_err("Binary measurement list too large.\n");
 107                 return;
 108         }
 109
 110         ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
 111                                   kexec_segment_size);
 112         if (!kexec_buffer) {
 113                 pr_err("Not enough memory for the kexec measurement buffer.\n");
 114                 return;
 115         }
 116
 117         kbuf.buffer = kexec_buffer;
 118         kbuf.bufsz = kexec_buffer_size;
 119         kbuf.memsz = kexec_segment_size;
 120         ret = kexec_add_buffer(&kbuf);
 121         if (ret) {
 122                 pr_err("Error passing over kexec measurement buffer.\n");
 123                 return;
 124         }
 125
 126         ret = arch_ima_add_kexec_buffer(image, kbuf.mem, kexec_segment_size);
 127         if (ret) {
 128                 pr_err("Error passing over kexec measurement buffer.\n");
 129                 return;
 130         }
 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 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 }