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 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 ret = machine_kexec_post_load(image);
163 if (ret)
164 goto out;
165
166 /* Install the new kernel and uninstall the old */
167 image = xchg(dest_image, image);
168
169 out:
170 if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
171 arch_kexec_protect_crashkres();
172
173 kimage_free(image);
174 return ret;
175 }
176
177 /*
178 * Exec Kernel system call: for obvious reasons only root may call it.
179 *
180 * This call breaks up into three pieces.
181 * - A generic part which loads the new kernel from the current
182 * address space, and very carefully places the data in the
183 * allocated pages.
184 *
185 * - A generic part that interacts with the kernel and tells all of
186 * the devices to shut down. Preventing on-going dmas, and placing
187 * the devices in a consistent state so a later kernel can
188 * reinitialize them.
189 *
190 * - A machine specific part that includes the syscall number
191 * and then copies the image to it's final destination. And
192 * jumps into the image at entry.
193 *
194 * kexec does not sync, or unmount filesystems so if you need
195 * that to happen you need to do that yourself.
196 */
197
kexec_load_check(unsigned long nr_segments,unsigned long flags)198 static inline int kexec_load_check(unsigned long nr_segments,
199 unsigned long flags)
200 {
201 int result;
202
203 /* We only trust the superuser with rebooting the system. */
204 if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
205 return -EPERM;
206
207 /* Permit LSMs and IMA to fail the kexec */
208 result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
209 if (result < 0)
210 return result;
211
212 /*
213 * kexec can be used to circumvent module loading restrictions, so
214 * prevent loading in that case
215 */
216 result = security_locked_down(LOCKDOWN_KEXEC);
217 if (result)
218 return result;
219
220 /*
221 * Verify we have a legal set of flags
222 * This leaves us room for future extensions.
223 */
224 if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
225 return -EINVAL;
226
227 /* Put an artificial cap on the number
228 * of segments passed to kexec_load.
229 */
230 if (nr_segments > KEXEC_SEGMENT_MAX)
231 return -EINVAL;
232
233 return 0;
234 }
235
SYSCALL_DEFINE4(kexec_load,unsigned long,entry,unsigned long,nr_segments,struct kexec_segment __user *,segments,unsigned long,flags)236 SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
237 struct kexec_segment __user *, segments, unsigned long, flags)
238 {
239 int 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 /* Because we write directly to the reserved memory
251 * region when loading crash kernels we need a mutex here to
252 * prevent multiple crash kernels from attempting to load
253 * simultaneously, and to prevent a crash kernel from loading
254 * over the top of a in use crash kernel.
255 *
256 * KISS: always take the mutex.
257 */
258 if (!mutex_trylock(&kexec_mutex))
259 return -EBUSY;
260
261 result = do_kexec_load(entry, nr_segments, segments, flags);
262
263 mutex_unlock(&kexec_mutex);
264
265 return result;
266 }
267
268 #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)269 COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
270 compat_ulong_t, nr_segments,
271 struct compat_kexec_segment __user *, segments,
272 compat_ulong_t, flags)
273 {
274 struct compat_kexec_segment in;
275 struct kexec_segment out, __user *ksegments;
276 unsigned long i, result;
277
278 result = kexec_load_check(nr_segments, flags);
279 if (result)
280 return result;
281
282 /* Don't allow clients that don't understand the native
283 * architecture to do anything.
284 */
285 if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT)
286 return -EINVAL;
287
288 ksegments = compat_alloc_user_space(nr_segments * sizeof(out));
289 for (i = 0; i < nr_segments; i++) {
290 result = copy_from_user(&in, &segments[i], sizeof(in));
291 if (result)
292 return -EFAULT;
293
294 out.buf = compat_ptr(in.buf);
295 out.bufsz = in.bufsz;
296 out.mem = in.mem;
297 out.memsz = in.memsz;
298
299 result = copy_to_user(&ksegments[i], &out, sizeof(out));
300 if (result)
301 return -EFAULT;
302 }
303
304 /* Because we write directly to the reserved memory
305 * region when loading crash kernels we need a mutex here to
306 * prevent multiple crash kernels from attempting to load
307 * simultaneously, and to prevent a crash kernel from loading
308 * over the top of a in use crash kernel.
309 *
310 * KISS: always take the mutex.
311 */
312 if (!mutex_trylock(&kexec_mutex))
313 return -EBUSY;
314
315 result = do_kexec_load(entry, nr_segments, ksegments, flags);
316
317 mutex_unlock(&kexec_mutex);
318
319 return result;
320 }
321 #endif
322
