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 copy_user_segment_list(struct kimage *image,
  23                                   unsigned long nr_segments,
  24                                   struct kexec_segment __user *segments)
  25 {
  26         int ret;
  27         size_t segment_bytes;
  28
  29         /* Read in the segments */
  30         image->nr_segments = nr_segments;
  31         segment_bytes = nr_segments * sizeof(*segments);
  32         ret = copy_from_user(image->segment, segments, segment_bytes);
  33         if (ret)
  34                 ret = -EFAULT;
  35
  36         return ret;
  37 }
  38
  39 static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
  40                              unsigned long nr_segments,
  41                              struct kexec_segment __user *segments,
  42                              unsigned long flags)
  43 {
  44         int ret;
  45         struct kimage *image;
  46         bool kexec_on_panic = flags & KEXEC_ON_CRASH;
  47
  48         if (kexec_on_panic) {
  49                 /* Verify we have a valid entry point */
  50                 if ((entry < phys_to_boot_phys(crashk_res.start)) ||
  51                     (entry > phys_to_boot_phys(crashk_res.end)))
  52                         return -EADDRNOTAVAIL;
  53         }
  54
  55         /* Allocate and initialize a controlling structure */
  56         image = do_kimage_alloc_init();
  57         if (!image)
  58                 return -ENOMEM;
  59
  60         image->start = entry;
  61
  62         ret = copy_user_segment_list(image, nr_segments, segments);
  63         if (ret)
  64                 goto out_free_image;
  65
  66         if (kexec_on_panic) {
  67                 /* Enable special crash kernel control page alloc policy. */
  68                 image->control_page = crashk_res.start;
  69                 image->type = KEXEC_TYPE_CRASH;
  70         }
  71
  72         ret = sanity_check_segment_list(image);
  73         if (ret)
  74                 goto out_free_image;
  75
  76         /*
  77          * Find a location for the control code buffer, and add it
  78          * the vector of segments so that it's pages will also be
  79          * counted as destination pages.
  80          */
  81         ret = -ENOMEM;
  82         image->control_code_page = kimage_alloc_control_pages(image,
  83                                            get_order(KEXEC_CONTROL_PAGE_SIZE));
  84         if (!image->control_code_page) {
  85                 pr_err("Could not allocate control_code_buffer\n");
  86                 goto out_free_image;
  87         }
  88
  89         if (!kexec_on_panic) {
  90                 image->swap_page = kimage_alloc_control_pages(image, 0);
  91                 if (!image->swap_page) {
  92                         pr_err("Could not allocate swap buffer\n");
  93                         goto out_free_control_pages;
  94                 }
  95         }
  96
  97         *rimage = image;
  98         return 0;
  99 out_free_control_pages:
 100         kimage_free_page_list(&image->control_pages);
 101 out_free_image:
 102         kfree(image);
 103         return ret;
 104 }
 105
 106 static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 107                 struct kexec_segment __user *segments, unsigned long flags)
 108 {
 109         struct kimage **dest_image, *image;
 110         unsigned long i;
 111         int ret;
 112
 113         if (flags & KEXEC_ON_CRASH) {
 114                 dest_image = &kexec_crash_image;
 115                 if (kexec_crash_image)
 116                         arch_kexec_unprotect_crashkres();
 117         } else {
 118                 dest_image = &kexec_image;
 119         }
 120
 121         if (nr_segments == 0) {
 122                 /* Uninstall image */
 123                 kimage_free(xchg(dest_image, NULL));
 124                 return 0;
 125         }
 126         if (flags & KEXEC_ON_CRASH) {
 127                 /*
 128                  * Loading another kernel to switch to if this one
 129                  * crashes.  Free any current crash dump kernel before
 130                  * we corrupt it.
 131                  */
 132                 kimage_free(xchg(&kexec_crash_image, NULL));
 133         }
 134
 135         ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
 136         if (ret)
 137                 return ret;
 138
 139         if (flags & KEXEC_PRESERVE_CONTEXT)
 140                 image->preserve_context = 1;
 141
 142         ret = machine_kexec_prepare(image);
 143         if (ret)
 144                 goto out;
 145
 146         /*
 147          * Some architecture(like S390) may touch the crash memory before
 148          * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
 149          */
 150         ret = kimage_crash_copy_vmcoreinfo(image);
 151         if (ret)
 152                 goto out;
 153
 154         for (i = 0; i < nr_segments; i++) {
 155                 ret = kimage_load_segment(image, &image->segment[i]);
 156                 if (ret)
 157                         goto out;
 158         }
 159
 160         kimage_terminate(image);
 161
 162         /* Install the new kernel and uninstall the old */
 163         image = xchg(dest_image, image);
 164
 165 out:
 166         if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
 167                 arch_kexec_protect_crashkres();
 168
 169         kimage_free(image);
 170         return ret;
 171 }
 172
 173 /*
 174  * Exec Kernel system call: for obvious reasons only root may call it.
 175  *
 176  * This call breaks up into three pieces.
 177  * - A generic part which loads the new kernel from the current
 178  *   address space, and very carefully places the data in the
 179  *   allocated pages.
 180  *
 181  * - A generic part that interacts with the kernel and tells all of
 182  *   the devices to shut down.  Preventing on-going dmas, and placing
 183  *   the devices in a consistent state so a later kernel can
 184  *   reinitialize them.
 185  *
 186  * - A machine specific part that includes the syscall number
 187  *   and then copies the image to it's final destination.  And
 188  *   jumps into the image at entry.
 189  *
 190  * kexec does not sync, or unmount filesystems so if you need
 191  * that to happen you need to do that yourself.
 192  */
 193
 194 static inline int kexec_load_check(unsigned long nr_segments,
 195                                    unsigned long flags)
 196 {
 197         int result;
 198
 199         /* We only trust the superuser with rebooting the system. */
 200         if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 201                 return -EPERM;
 202
 203         /* Permit LSMs and IMA to fail the kexec */
 204         result = security_kernel_load_data(LOADING_KEXEC_IMAGE);
 205         if (result < 0)
 206                 return result;
 207
 208         /*
 209          * kexec can be used to circumvent module loading restrictions, so
 210          * prevent loading in that case
 211          */
 212         result = security_locked_down(LOCKDOWN_KEXEC);
 213         if (result)
 214                 return result;
 215
 216         /*
 217          * Verify we have a legal set of flags
 218          * This leaves us room for future extensions.
 219          */
 220         if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
 221                 return -EINVAL;
 222
 223         /* Put an artificial cap on the number
 224          * of segments passed to kexec_load.
 225          */
 226         if (nr_segments > KEXEC_SEGMENT_MAX)
 227                 return -EINVAL;
 228
 229         return 0;
 230 }
 231
 232 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 233                 struct kexec_segment __user *, segments, unsigned long, flags)
 234 {
 235         int 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         /* Because we write directly to the reserved memory
 247          * region when loading crash kernels we need a mutex here to
 248          * prevent multiple crash  kernels from attempting to load
 249          * simultaneously, and to prevent a crash kernel from loading
 250          * over the top of a in use crash kernel.
 251          *
 252          * KISS: always take the mutex.
 253          */
 254         if (!mutex_trylock(&kexec_mutex))
 255                 return -EBUSY;
 256
 257         result = do_kexec_load(entry, nr_segments, segments, flags);
 258
 259         mutex_unlock(&kexec_mutex);
 260
 261         return result;
 262 }
 263
 264 #ifdef CONFIG_COMPAT
 265 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 266                        compat_ulong_t, nr_segments,
 267                        struct compat_kexec_segment __user *, segments,
 268                        compat_ulong_t, flags)
 269 {
 270         struct compat_kexec_segment in;
 271         struct kexec_segment out, __user *ksegments;
 272         unsigned long i, result;
 273
 274         result = kexec_load_check(nr_segments, flags);
 275         if (result)
 276                 return result;
 277
 278         /* Don't allow clients that don't understand the native
 279          * architecture to do anything.
 280          */
 281         if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
 282                 return -EINVAL;
 283
 284         ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
 285         for (i = 0; i < nr_segments; i++) {
 286                 result = copy_from_user(&in, &segments[i], sizeof(in));
 287                 if (result)
 288                         return -EFAULT;
 289
 290                 out.buf   = compat_ptr(in.buf);
 291                 out.bufsz = in.bufsz;
 292                 out.mem   = in.mem;
 293                 out.memsz = in.memsz;
 294
 295                 result = copy_to_user(&ksegments[i], &out, sizeof(out));
 296                 if (result)
 297                         return -EFAULT;
 298         }
 299
 300         /* Because we write directly to the reserved memory
 301          * region when loading crash kernels we need a mutex here to
 302          * prevent multiple crash  kernels from attempting to load
 303          * simultaneously, and to prevent a crash kernel from loading
 304          * over the top of a in use crash kernel.
 305          *
 306          * KISS: always take the mutex.
 307          */
 308         if (!mutex_trylock(&kexec_mutex))
 309                 return -EBUSY;
 310
 311         result = do_kexec_load(entry, nr_segments, ksegments, flags);
 312
 313         mutex_unlock(&kexec_mutex);
 314
 315         return result;
 316 }
 317 #endif