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
copy_user_segment_list(struct kimage * image,unsigned long nr_segments,struct kexec_segment __user * segments)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
kimage_alloc_init(struct kimage ** rimage,unsigned long entry,unsigned long nr_segments,struct kexec_segment __user * segments,unsigned long flags)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
do_kexec_load(unsigned long entry,unsigned long nr_segments,struct kexec_segment __user * segments,unsigned long flags)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 /*
114 * Because we write directly to the reserved memory region when loading
115 * crash kernels we need a serialization here to prevent multiple crash
116 * kernels from attempting to load simultaneously.
117 */
118 if (!kexec_trylock())
119 return -EBUSY;
120
121 if (flags & KEXEC_ON_CRASH) {
122 dest_image = &kexec_crash_image;
123 if (kexec_crash_image)
124 arch_kexec_unprotect_crashkres();
125 } else {
126 dest_image = &kexec_image;
127 }
128
129 if (nr_segments == 0) {
130 /* Uninstall image */
131 kimage_free(xchg(dest_image, NULL));
132 ret = 0;
133 goto out_unlock;
134 }
135 if (flags & KEXEC_ON_CRASH) {
136 /*
137 * Loading another kernel to switch to if this one
138 * crashes. Free any current crash dump kernel before
139 * we corrupt it.
140 */
141 kimage_free(xchg(&kexec_crash_image, NULL));
142 }
143
144 ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
145 if (ret)
146 goto out_unlock;
147
148 if (flags & KEXEC_PRESERVE_CONTEXT)
149 image->preserve_context = 1;
150
151 ret = machine_kexec_prepare(image);
152 if (ret)
153 goto out;
154
155 /*
156 * Some architecture(like S390) may touch the crash memory before
157 * machine_kexec_prepare(), we must copy vmcoreinfo data after it.
158 */
159 ret = kimage_crash_copy_vmcoreinfo(image);
160 if (ret)
161 goto out;
162
163 for (i = 0; i < nr_segments; i++) {
164 ret = kimage_load_segment(image, &image->segment[i]);
165 if (ret)
166 goto out;
167 }
168
169 kimage_terminate(image);
170
171 ret = machine_kexec_post_load(image);
172 if (ret)
173 goto out;
174
175 /* Install the new kernel and uninstall the old */
176 image = xchg(dest_image, image);
177
178 out:
179 if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
180 arch_kexec_protect_crashkres();
181
182 kimage_free(image);
183 out_unlock:
184 kexec_unlock();
185 return ret;
186 }
187
188 /*
189 * Exec Kernel system call: for obvious reasons only root may call it.
190 *
191 * This call breaks up into three pieces.
192 * - A generic part which loads the new kernel from the current
193 * address space, and very carefully places the data in the
194 * allocated pages.
195 *
196 * - A generic part that interacts with the kernel and tells all of
197 * the devices to shut down. Preventing on-going dmas, and placing
198 * the devices in a consistent state so a later kernel can
199 * reinitialize them.
200 *
201 * - A machine specific part that includes the syscall number
202 * and then copies the image to it's final destination. And
203 * jumps into the image at entry.
204 *
205 * kexec does not sync, or unmount filesystems so if you need
206 * that to happen you need to do that yourself.
207 */
208
kexec_load_check(unsigned long nr_segments,unsigned long flags)209 static inline int kexec_load_check(unsigned long nr_segments,
210 unsigned long flags)
211 {
212 int result;
213
214 /* We only trust the superuser with rebooting the system. */
215 if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
216 return -EPERM;
217
218 /* Permit LSMs and IMA to fail the kexec */
219 result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
220 if (result < 0)
221 return result;
222
223 /*
224 * kexec can be used to circumvent module loading restrictions, so
225 * prevent loading in that case
226 */
227 result = security_locked_down(LOCKDOWN_KEXEC);
228 if (result)
229 return result;
230
231 /*
232 * Verify we have a legal set of flags
233 * This leaves us room for future extensions.
234 */
235 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
236 return -EINVAL;
237
238 /* Put an artificial cap on the number
239 * of segments passed to kexec_load.
240 */
241 if (nr_segments > KEXEC_SEGMENT_MAX)
242 return -EINVAL;
243
244 return 0;
245 }
246
SYSCALL_DEFINE4(kexec_load,unsigned long,entry,unsigned long,nr_segments,struct kexec_segment __user *,segments,unsigned long,flags)247 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
248 struct kexec_segment __user *, segments, unsigned long, flags)
249 {
250 int result;
251
252 result = kexec_load_check(nr_segments, flags);
253 if (result)
254 return result;
255
256 /* Verify we are on the appropriate architecture */
257 if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) &&
258 ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT))
259 return -EINVAL;
260
261 result = do_kexec_load(entry, nr_segments, segments, flags);
262
263 return result;
264 }
265
266 #ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(kexec_load,compat_ulong_t,entry,compat_ulong_t,nr_segments,struct compat_kexec_segment __user *,segments,compat_ulong_t,flags)267 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
268 compat_ulong_t, nr_segments,
269 struct compat_kexec_segment __user *, segments,
270 compat_ulong_t, flags)
271 {
272 struct compat_kexec_segment in;
273 struct kexec_segment out, __user *ksegments;
274 unsigned long i, result;
275
276 result = kexec_load_check(nr_segments, flags);
277 if (result)
278 return result;
279
280 /* Don't allow clients that don't understand the native
281 * architecture to do anything.
282 */
283 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
284 return -EINVAL;
285
286 ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
287 for (i = 0; i < nr_segments; i++) {
288 result = copy_from_user(&in, &segments[i], sizeof(in));
289 if (result)
290 return -EFAULT;
291
292 out.buf = compat_ptr(in.buf);
293 out.bufsz = in.bufsz;
294 out.mem = in.mem;
295 out.memsz = in.memsz;
296
297 result = copy_to_user(&ksegments[i], &out, sizeof(out));
298 if (result)
299 return -EFAULT;
300 }
301
302 result = do_kexec_load(entry, nr_segments, ksegments, flags);
303
304 return result;
305 }
306 #endif
307