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 mutex here to prevent multiple crash kernels
  97          * from attempting to load simultaneously, and to prevent a crash kernel
  98          * from loading over the top of a in use crash kernel.
  99          *
 100          * KISS: always take the mutex.
 101          */
 102         if (!mutex_trylock(&kexec_mutex))
 103                 return -EBUSY;
 104
 105         if (flags & KEXEC_ON_CRASH) {
 106                 dest_image = &kexec_crash_image;
 107                 if (kexec_crash_image)
 108                         arch_kexec_unprotect_crashkres();
 109         } else {
 110                 dest_image = &kexec_image;
 111         }
 112
 113         if (nr_segments == 0) {
 114                 /* Uninstall image */
 115                 kimage_free(xchg(dest_image, NULL));
 116                 ret = 0;
 117                 goto out_unlock;
 118         }
 119         if (flags & KEXEC_ON_CRASH) {
 120                 /*
 121                  * Loading another kernel to switch to if this one
 122                  * crashes.  Free any current crash dump kernel before
 123                  * we corrupt it.
 124                  */
 125                 kimage_free(xchg(&kexec_crash_image, NULL));
 126         }
 127
 128         ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
 129         if (ret)
 130                 goto out_unlock;
 131
 132         if (flags & KEXEC_PRESERVE_CONTEXT)
 133                 image->preserve_context = 1;
 134
 135         ret = machine_kexec_prepare(image);
 136         if (ret)
 137                 goto out;
 138
 139         /*
 140          * Some architecture(like S390) may touch the crash memory before
 141          * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
 142          */
 143         ret = kimage_crash_copy_vmcoreinfo(image);
 144         if (ret)
 145                 goto out;
 146
 147         for (i = 0; i < nr_segments; i++) {
 148                 ret = kimage_load_segment(image, &image->segment[i]);
 149                 if (ret)
 150                         goto out;
 151         }
 152
 153         kimage_terminate(image);
 154
 155         ret = machine_kexec_post_load(image);
 156         if (ret)
 157                 goto out;
 158
 159         /* Install the new kernel and uninstall the old */
 160         image = xchg(dest_image, image);
 161
 162 out:
 163         if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
 164                 arch_kexec_protect_crashkres();
 165
 166         kimage_free(image);
 167 out_unlock:
 168         mutex_unlock(&kexec_mutex);
 169         return ret;
 170 }
 171
 172 /*
 173  * Exec Kernel system call: for obvious reasons only root may call it.
 174  *
 175  * This call breaks up into three pieces.
 176  * - A generic part which loads the new kernel from the current
 177  *   address space, and very carefully places the data in the
 178  *   allocated pages.
 179  *
 180  * - A generic part that interacts with the kernel and tells all of
 181  *   the devices to shut down.  Preventing on-going dmas, and placing
 182  *   the devices in a consistent state so a later kernel can
 183  *   reinitialize them.
 184  *
 185  * - A machine specific part that includes the syscall number
 186  *   and then copies the image to it's final destination.  And
 187  *   jumps into the image at entry.
 188  *
 189  * kexec does not sync, or unmount filesystems so if you need
 190  * that to happen you need to do that yourself.
 191  */
 192
 193 static inline int kexec_load_check(unsigned long nr_segments,
 194                                    unsigned long flags)
 195 {
 196         int result;
 197
 198         /* We only trust the superuser with rebooting the system. */
 199         if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 200                 return -EPERM;
 201
 202         /* Permit LSMs and IMA to fail the kexec */
 203         result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
 204         if (result < 0)
 205                 return result;
 206
 207         /*
 208          * kexec can be used to circumvent module loading restrictions, so
 209          * prevent loading in that case
 210          */
 211         result = security_locked_down(LOCKDOWN_KEXEC);
 212         if (result)
 213                 return result;
 214
 215         /*
 216          * Verify we have a legal set of flags
 217          * This leaves us room for future extensions.
 218          */
 219         if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
 220                 return -EINVAL;
 221
 222         /* Put an artificial cap on the number
 223          * of segments passed to kexec_load.
 224          */
 225         if (nr_segments > KEXEC_SEGMENT_MAX)
 226                 return -EINVAL;
 227
 228         return 0;
 229 }
 230
 231 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 232                 struct kexec_segment __user *, segments, unsigned long, flags)
 233 {
 234         struct kexec_segment *ksegments;
 235         unsigned long result;
 236
 237         result = kexec_load_check(nr_segments, flags);
 238         if (result)
 239                 return result;
 240
 241         /* Verify we are on the appropriate architecture */
 242         if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
 243                 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
 244                 return -EINVAL;
 245
 246         ksegments = memdup_user(segments, nr_segments * sizeof(ksegments[0]));
 247         if (IS_ERR(ksegments))
 248                 return PTR_ERR(ksegments);
 249
 250         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 251         kfree(ksegments);
 252
 253         return result;
 254 }
 255
 256 #ifdef CONFIG_COMPAT
 257 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 258                        compat_ulong_t, nr_segments,
 259                        struct compat_kexec_segment __user *, segments,
 260                        compat_ulong_t, flags)
 261 {
 262         struct compat_kexec_segment in;
 263         struct kexec_segment *ksegments;
 264         unsigned long i, result;
 265
 266         result = kexec_load_check(nr_segments, flags);
 267         if (result)
 268                 return result;
 269
 270         /* Don't allow clients that don't understand the native
 271          * architecture to do anything.
 272          */
 273         if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
 274                 return -EINVAL;
 275
 276         ksegments = kmalloc_array(nr_segments, sizeof(ksegments[0]),
 277                         GFP_KERNEL);
 278         if (!ksegments)
 279                 return -ENOMEM;
 280
 281         for (i = 0; i < nr_segments; i++) {
 282                 result = copy_from_user(&in, &segments[i], sizeof(in));
 283                 if (result)
 284                         goto fail;
 285
 286                 ksegments[i].buf   = compat_ptr(in.buf);
 287                 ksegments[i].bufsz = in.bufsz;
 288                 ksegments[i].mem   = in.mem;
 289                 ksegments[i].memsz = in.memsz;
 290         }
 291
 292         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 293
 294 fail:
 295         kfree(ksegments);
 296         return result;
 297 }
 298 #endif