1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * fail_function.c: Function-based error injection
4 */
5 #include <linux/error-injection.h>
6 #include <linux/debugfs.h>
7 #include <linux/fault-inject.h>
8 #include <linux/kallsyms.h>
9 #include <linux/kprobes.h>
10 #include <linux/module.h>
11 #include <linux/mutex.h>
12 #include <linux/slab.h>
13 #include <linux/uaccess.h>
14
15 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
16
fei_post_handler(struct kprobe * kp,struct pt_regs * regs,unsigned long flags)17 static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
18 unsigned long flags)
19 {
20 /*
21 * A dummy post handler is required to prohibit optimizing, because
22 * jump optimization does not support execution path overriding.
23 */
24 }
25
26 struct fei_attr {
27 struct list_head list;
28 struct kprobe kp;
29 unsigned long retval;
30 };
31 static DEFINE_MUTEX(fei_lock);
32 static LIST_HEAD(fei_attr_list);
33 static DECLARE_FAULT_ATTR(fei_fault_attr);
34 static struct dentry *fei_debugfs_dir;
35
adjust_error_retval(unsigned long addr,unsigned long retv)36 static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
37 {
38 switch (get_injectable_error_type(addr)) {
39 case EI_ETYPE_NULL:
40 if (retv != 0)
41 return 0;
42 break;
43 case EI_ETYPE_ERRNO:
44 if (retv < (unsigned long)-MAX_ERRNO)
45 return (unsigned long)-EINVAL;
46 break;
47 case EI_ETYPE_ERRNO_NULL:
48 if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
49 return (unsigned long)-EINVAL;
50 break;
51 }
52
53 return retv;
54 }
55
fei_attr_new(const char * sym,unsigned long addr)56 static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
57 {
58 struct fei_attr *attr;
59
60 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
61 if (attr) {
62 attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
63 if (!attr->kp.symbol_name) {
64 kfree(attr);
65 return NULL;
66 }
67 attr->kp.pre_handler = fei_kprobe_handler;
68 attr->kp.post_handler = fei_post_handler;
69 attr->retval = adjust_error_retval(addr, 0);
70 INIT_LIST_HEAD(&attr->list);
71 }
72 return attr;
73 }
74
fei_attr_free(struct fei_attr * attr)75 static void fei_attr_free(struct fei_attr *attr)
76 {
77 if (attr) {
78 kfree(attr->kp.symbol_name);
79 kfree(attr);
80 }
81 }
82
fei_attr_lookup(const char * sym)83 static struct fei_attr *fei_attr_lookup(const char *sym)
84 {
85 struct fei_attr *attr;
86
87 list_for_each_entry(attr, &fei_attr_list, list) {
88 if (!strcmp(attr->kp.symbol_name, sym))
89 return attr;
90 }
91
92 return NULL;
93 }
94
fei_attr_is_valid(struct fei_attr * _attr)95 static bool fei_attr_is_valid(struct fei_attr *_attr)
96 {
97 struct fei_attr *attr;
98
99 list_for_each_entry(attr, &fei_attr_list, list) {
100 if (attr == _attr)
101 return true;
102 }
103
104 return false;
105 }
106
fei_retval_set(void * data,u64 val)107 static int fei_retval_set(void *data, u64 val)
108 {
109 struct fei_attr *attr = data;
110 unsigned long retv = (unsigned long)val;
111 int err = 0;
112
113 mutex_lock(&fei_lock);
114 /*
115 * Since this operation can be done after retval file is removed,
116 * It is safer to check the attr is still valid before accessing
117 * its member.
118 */
119 if (!fei_attr_is_valid(attr)) {
120 err = -ENOENT;
121 goto out;
122 }
123
124 if (attr->kp.addr) {
125 if (adjust_error_retval((unsigned long)attr->kp.addr,
126 val) != retv)
127 err = -EINVAL;
128 }
129 if (!err)
130 attr->retval = val;
131 out:
132 mutex_unlock(&fei_lock);
133
134 return err;
135 }
136
fei_retval_get(void * data,u64 * val)137 static int fei_retval_get(void *data, u64 *val)
138 {
139 struct fei_attr *attr = data;
140 int err = 0;
141
142 mutex_lock(&fei_lock);
143 /* Here we also validate @attr to ensure it still exists. */
144 if (!fei_attr_is_valid(attr))
145 err = -ENOENT;
146 else
147 *val = attr->retval;
148 mutex_unlock(&fei_lock);
149
150 return err;
151 }
152 DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
153 "%llx\n");
154
fei_debugfs_add_attr(struct fei_attr * attr)155 static void fei_debugfs_add_attr(struct fei_attr *attr)
156 {
157 struct dentry *dir;
158
159 dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
160
161 debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops);
162 }
163
fei_debugfs_remove_attr(struct fei_attr * attr)164 static void fei_debugfs_remove_attr(struct fei_attr *attr)
165 {
166 struct dentry *dir;
167
168 dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
169 debugfs_remove_recursive(dir);
170 }
171
fei_kprobe_handler(struct kprobe * kp,struct pt_regs * regs)172 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
173 {
174 struct fei_attr *attr = container_of(kp, struct fei_attr, kp);
175
176 if (should_fail(&fei_fault_attr, 1)) {
177 regs_set_return_value(regs, attr->retval);
178 override_function_with_return(regs);
179 return 1;
180 }
181
182 return 0;
183 }
NOKPROBE_SYMBOL(fei_kprobe_handler)184 NOKPROBE_SYMBOL(fei_kprobe_handler)
185
186 static void *fei_seq_start(struct seq_file *m, loff_t *pos)
187 {
188 mutex_lock(&fei_lock);
189 return seq_list_start(&fei_attr_list, *pos);
190 }
191
fei_seq_stop(struct seq_file * m,void * v)192 static void fei_seq_stop(struct seq_file *m, void *v)
193 {
194 mutex_unlock(&fei_lock);
195 }
196
fei_seq_next(struct seq_file * m,void * v,loff_t * pos)197 static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos)
198 {
199 return seq_list_next(v, &fei_attr_list, pos);
200 }
201
fei_seq_show(struct seq_file * m,void * v)202 static int fei_seq_show(struct seq_file *m, void *v)
203 {
204 struct fei_attr *attr = list_entry(v, struct fei_attr, list);
205
206 seq_printf(m, "%ps\n", attr->kp.addr);
207 return 0;
208 }
209
210 static const struct seq_operations fei_seq_ops = {
211 .start = fei_seq_start,
212 .next = fei_seq_next,
213 .stop = fei_seq_stop,
214 .show = fei_seq_show,
215 };
216
fei_open(struct inode * inode,struct file * file)217 static int fei_open(struct inode *inode, struct file *file)
218 {
219 return seq_open(file, &fei_seq_ops);
220 }
221
fei_attr_remove(struct fei_attr * attr)222 static void fei_attr_remove(struct fei_attr *attr)
223 {
224 fei_debugfs_remove_attr(attr);
225 unregister_kprobe(&attr->kp);
226 list_del(&attr->list);
227 fei_attr_free(attr);
228 }
229
fei_attr_remove_all(void)230 static void fei_attr_remove_all(void)
231 {
232 struct fei_attr *attr, *n;
233
234 list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
235 fei_attr_remove(attr);
236 }
237 }
238
fei_write(struct file * file,const char __user * buffer,size_t count,loff_t * ppos)239 static ssize_t fei_write(struct file *file, const char __user *buffer,
240 size_t count, loff_t *ppos)
241 {
242 struct fei_attr *attr;
243 unsigned long addr;
244 char *buf, *sym;
245 int ret;
246
247 /* cut off if it is too long */
248 if (count > KSYM_NAME_LEN)
249 count = KSYM_NAME_LEN;
250 buf = kmalloc(count + 1, GFP_KERNEL);
251 if (!buf)
252 return -ENOMEM;
253
254 if (copy_from_user(buf, buffer, count)) {
255 ret = -EFAULT;
256 goto out;
257 }
258 buf[count] = '\0';
259 sym = strstrip(buf);
260
261 mutex_lock(&fei_lock);
262
263 /* Writing just spaces will remove all injection points */
264 if (sym[0] == '\0') {
265 fei_attr_remove_all();
266 ret = count;
267 goto out;
268 }
269 /* Writing !function will remove one injection point */
270 if (sym[0] == '!') {
271 attr = fei_attr_lookup(sym + 1);
272 if (!attr) {
273 ret = -ENOENT;
274 goto out;
275 }
276 fei_attr_remove(attr);
277 ret = count;
278 goto out;
279 }
280
281 addr = kallsyms_lookup_name(sym);
282 if (!addr) {
283 ret = -EINVAL;
284 goto out;
285 }
286 if (!within_error_injection_list(addr)) {
287 ret = -ERANGE;
288 goto out;
289 }
290 if (fei_attr_lookup(sym)) {
291 ret = -EBUSY;
292 goto out;
293 }
294 attr = fei_attr_new(sym, addr);
295 if (!attr) {
296 ret = -ENOMEM;
297 goto out;
298 }
299
300 ret = register_kprobe(&attr->kp);
301 if (!ret)
302 fei_debugfs_add_attr(attr);
303 if (ret < 0)
304 fei_attr_remove(attr);
305 else {
306 list_add_tail(&attr->list, &fei_attr_list);
307 ret = count;
308 }
309 out:
310 kfree(buf);
311 mutex_unlock(&fei_lock);
312 return ret;
313 }
314
315 static const struct file_operations fei_ops = {
316 .open = fei_open,
317 .read = seq_read,
318 .write = fei_write,
319 .llseek = seq_lseek,
320 .release = seq_release,
321 };
322
fei_debugfs_init(void)323 static int __init fei_debugfs_init(void)
324 {
325 struct dentry *dir;
326
327 dir = fault_create_debugfs_attr("fail_function", NULL,
328 &fei_fault_attr);
329 if (IS_ERR(dir))
330 return PTR_ERR(dir);
331
332 /* injectable attribute is just a symlink of error_inject/list */
333 debugfs_create_symlink("injectable", dir, "../error_injection/list");
334
335 debugfs_create_file("inject", 0600, dir, NULL, &fei_ops);
336
337 fei_debugfs_dir = dir;
338
339 return 0;
340 }
341
342 late_initcall(fei_debugfs_init);
343