kernel/kexec.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * kexec.c - kexec_load system call
   4  * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
   5  */
   6
   7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/capability.h>
  10 #include <linux/mm.h>
  11 #include <linux/file.h>
  12 #include <linux/security.h>
  13 #include <linux/kexec.h>
  14 #include <linux/mutex.h>
  15 #include <linux/list.h>
  16 #include <linux/syscalls.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/slab.h>
  19
  20 #include "kexec_internal.h"
  21
  22 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
  23                              unsigned long nr_segments,
  24                              struct kexec_segment *segments,
  25                              unsigned long flags)
  26 {
  27         int ret;
  28         struct kimage *image;
  29         bool kexec_on_panic = flags & KEXEC_ON_CRASH;
  30
  31         if (kexec_on_panic) {
  32                 /* Verify we have a valid entry point */
  33                 if ((entry < phys_to_boot_phys(crashk_res.start)) ||
  34                     (entry > phys_to_boot_phys(crashk_res.end)))
  35                         return -EADDRNOTAVAIL;
  36         }
  37
  38         /* Allocate and initialize a controlling structure */
  39         image = do_kimage_alloc_init();
  40         if (!image)
  41                 return -ENOMEM;
  42
  43         image->start = entry;
  44         image->nr_segments = nr_segments;
  45         memcpy(image->segment, segments, nr_segments * sizeof(*segments));
  46
  47         if (kexec_on_panic) {
  48                 /* Enable special crash kernel control page alloc policy. */
  49                 image->control_page = crashk_res.start;
  50                 image->type = KEXEC_TYPE_CRASH;
  51         }
  52
  53         ret = sanity_check_segment_list(image);
  54         if (ret)
  55                 goto out_free_image;
  56
  57         /*
  58          * Find a location for the control code buffer, and add it
  59          * the vector of segments so that it's pages will also be
  60          * counted as destination pages.
  61          */
  62         ret = -ENOMEM;
  63         image->control_code_page = kimage_alloc_control_pages(image,
  64                                            get_order(KEXEC_CONTROL_PAGE_SIZE));
  65         if (!image->control_code_page) {
  66                 pr_err("Could not allocate control_code_buffer\n");
  67                 goto out_free_image;
  68         }
  69
  70         if (!kexec_on_panic) {
  71                 image->swap_page = kimage_alloc_control_pages(image, 0);
  72                 if (!image->swap_page) {
  73                         pr_err("Could not allocate swap buffer\n");
  74                         goto out_free_control_pages;
  75                 }
  76         }
  77
  78         *rimage = image;
  79         return 0;
  80 out_free_control_pages:
  81         kimage_free_page_list(&image->control_pages);
  82 out_free_image:
  83         kfree(image);
  84         return ret;
  85 }
  86
  87 static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
  88                 struct kexec_segment *segments, unsigned long flags)
  89 {
  90         struct kimage **dest_image, *image;
  91         unsigned long i;
  92         int ret;
  93
  94         /*
  95          * Because we write directly to the reserved memory region when loading
  96          * crash kernels we need a serialization here to prevent multiple crash
  97          * kernels from attempting to load simultaneously.
  98          */
  99         if (!kexec_trylock())
 100                 return -EBUSY;
 101
 102         if (flags & KEXEC_ON_CRASH) {
 103                 dest_image = &kexec_crash_image;
 104                 if (kexec_crash_image)
 105                         arch_kexec_unprotect_crashkres();
 106         } else {
 107                 dest_image = &kexec_image;
 108         }
 109
 110         if (nr_segments == 0) {
 111                 /* Uninstall image */
 112                 kimage_free(xchg(dest_image, NULL));
 113                 ret = 0;
 114                 goto out_unlock;
 115         }
 116         if (flags & KEXEC_ON_CRASH) {
 117                 /*
 118                  * Loading another kernel to switch to if this one
 119                  * crashes.  Free any current crash dump kernel before
 120                  * we corrupt it.
 121                  */
 122                 kimage_free(xchg(&kexec_crash_image, NULL));
 123         }
 124
 125         ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
 126         if (ret)
 127                 goto out_unlock;
 128
 129         if (flags & KEXEC_PRESERVE_CONTEXT)
 130                 image->preserve_context = 1;
 131
 132         ret = machine_kexec_prepare(image);
 133         if (ret)
 134                 goto out;
 135
 136         /*
 137          * Some architecture(like S390) may touch the crash memory before
 138          * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
 139          */
 140         ret = kimage_crash_copy_vmcoreinfo(image);
 141         if (ret)
 142                 goto out;
 143
 144         for (i = 0; i < nr_segments; i++) {
 145                 ret = kimage_load_segment(image, &image->segment[i]);
 146                 if (ret)
 147                         goto out;
 148         }
 149
 150         kimage_terminate(image);
 151
 152         ret = machine_kexec_post_load(image);
 153         if (ret)
 154                 goto out;
 155
 156         /* Install the new kernel and uninstall the old */
 157         image = xchg(dest_image, image);
 158
 159 out:
 160         if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
 161                 arch_kexec_protect_crashkres();
 162
 163         kimage_free(image);
 164 out_unlock:
 165         kexec_unlock();
 166         return ret;
 167 }
 168
 169 /*
 170  * Exec Kernel system call: for obvious reasons only root may call it.
 171  *
 172  * This call breaks up into three pieces.
 173  * - A generic part which loads the new kernel from the current
 174  *   address space, and very carefully places the data in the
 175  *   allocated pages.
 176  *
 177  * - A generic part that interacts with the kernel and tells all of
 178  *   the devices to shut down.  Preventing on-going dmas, and placing
 179  *   the devices in a consistent state so a later kernel can
 180  *   reinitialize them.
 181  *
 182  * - A machine specific part that includes the syscall number
 183  *   and then copies the image to it's final destination.  And
 184  *   jumps into the image at entry.
 185  *
 186  * kexec does not sync, or unmount filesystems so if you need
 187  * that to happen you need to do that yourself.
 188  */
 189
 190 static inline int kexec_load_check(unsigned long nr_segments,
 191                                    unsigned long flags)
 192 {
 193         int result;
 194
 195         /* We only trust the superuser with rebooting the system. */
 196         if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 197                 return -EPERM;
 198
 199         /* Permit LSMs and IMA to fail the kexec */
 200         result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
 201         if (result < 0)
 202                 return result;
 203
 204         /*
 205          * kexec can be used to circumvent module loading restrictions, so
 206          * prevent loading in that case
 207          */
 208         result = security_locked_down(LOCKDOWN_KEXEC);
 209         if (result)
 210                 return result;
 211
 212         /*
 213          * Verify we have a legal set of flags
 214          * This leaves us room for future extensions.
 215          */
 216         if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
 217                 return -EINVAL;
 218
 219         /* Put an artificial cap on the number
 220          * of segments passed to kexec_load.
 221          */
 222         if (nr_segments > KEXEC_SEGMENT_MAX)
 223                 return -EINVAL;
 224
 225         return 0;
 226 }
 227
 228 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 229                 struct kexec_segment __user *, segments, unsigned long, flags)
 230 {
 231         struct kexec_segment *ksegments;
 232         unsigned long result;
 233
 234         result = kexec_load_check(nr_segments, flags);
 235         if (result)
 236                 return result;
 237
 238         /* Verify we are on the appropriate architecture */
 239         if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
 240                 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
 241                 return -EINVAL;
 242
 243         ksegments = memdup_user(segments, nr_segments * sizeof(ksegments[0]));
 244         if (IS_ERR(ksegments))
 245                 return PTR_ERR(ksegments);
 246
 247         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 248         kfree(ksegments);
 249
 250         return result;
 251 }
 252
 253 #ifdef CONFIG_COMPAT
 254 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 255                        compat_ulong_t, nr_segments,
 256                        struct compat_kexec_segment __user *, segments,
 257                        compat_ulong_t, flags)
 258 {
 259         struct compat_kexec_segment in;
 260         struct kexec_segment *ksegments;
 261         unsigned long i, result;
 262
 263         result = kexec_load_check(nr_segments, flags);
 264         if (result)
 265                 return result;
 266
 267         /* Don't allow clients that don't understand the native
 268          * architecture to do anything.
 269          */
 270         if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
 271                 return -EINVAL;
 272
 273         ksegments = kmalloc_array(nr_segments, sizeof(ksegments[0]),
 274                         GFP_KERNEL);
 275         if (!ksegments)
 276                 return -ENOMEM;
 277
 278         for (i = 0; i < nr_segments; i++) {
 279                 result = copy_from_user(&in, &segments[i], sizeof(in));
 280                 if (result)
 281                         goto fail;
 282
 283                 ksegments[i].buf   = compat_ptr(in.buf);
 284                 ksegments[i].bufsz = in.bufsz;
 285                 ksegments[i].mem   = in.mem;
 286                 ksegments[i].memsz = in.memsz;
 287         }
 288
 289         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 290
 291 fail:
 292         kfree(ksegments);
 293         return result;
 294 }
 295 #endif