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