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 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 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 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 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 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 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 } 106 107 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 } 136 137 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"); 154 155 static int 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 if (!dir) 161 return -ENOMEM; 162 163 if (!debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops)) { 164 debugfs_remove_recursive(dir); 165 return -ENOMEM; 166 } 167 168 return 0; 169 } 170 171 static void fei_debugfs_remove_attr(struct fei_attr *attr) 172 { 173 struct dentry *dir; 174 175 dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir); 176 debugfs_remove_recursive(dir); 177 } 178 179 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs) 180 { 181 struct fei_attr *attr = container_of(kp, struct fei_attr, kp); 182 183 if (should_fail(&fei_fault_attr, 1)) { 184 regs_set_return_value(regs, attr->retval); 185 override_function_with_return(regs); 186 return 1; 187 } 188 189 return 0; 190 } 191 NOKPROBE_SYMBOL(fei_kprobe_handler) 192 193 static void *fei_seq_start(struct seq_file *m, loff_t *pos) 194 { 195 mutex_lock(&fei_lock); 196 return seq_list_start(&fei_attr_list, *pos); 197 } 198 199 static void fei_seq_stop(struct seq_file *m, void *v) 200 { 201 mutex_unlock(&fei_lock); 202 } 203 204 static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos) 205 { 206 return seq_list_next(v, &fei_attr_list, pos); 207 } 208 209 static int fei_seq_show(struct seq_file *m, void *v) 210 { 211 struct fei_attr *attr = list_entry(v, struct fei_attr, list); 212 213 seq_printf(m, "%pf\n", attr->kp.addr); 214 return 0; 215 } 216 217 static const struct seq_operations fei_seq_ops = { 218 .start = fei_seq_start, 219 .next = fei_seq_next, 220 .stop = fei_seq_stop, 221 .show = fei_seq_show, 222 }; 223 224 static int fei_open(struct inode *inode, struct file *file) 225 { 226 return seq_open(file, &fei_seq_ops); 227 } 228 229 static void fei_attr_remove(struct fei_attr *attr) 230 { 231 fei_debugfs_remove_attr(attr); 232 unregister_kprobe(&attr->kp); 233 list_del(&attr->list); 234 fei_attr_free(attr); 235 } 236 237 static void fei_attr_remove_all(void) 238 { 239 struct fei_attr *attr, *n; 240 241 list_for_each_entry_safe(attr, n, &fei_attr_list, list) { 242 fei_attr_remove(attr); 243 } 244 } 245 246 static ssize_t fei_write(struct file *file, const char __user *buffer, 247 size_t count, loff_t *ppos) 248 { 249 struct fei_attr *attr; 250 unsigned long addr; 251 char *buf, *sym; 252 int ret; 253 254 /* cut off if it is too long */ 255 if (count > KSYM_NAME_LEN) 256 count = KSYM_NAME_LEN; 257 buf = kmalloc(count + 1, GFP_KERNEL); 258 if (!buf) 259 return -ENOMEM; 260 261 if (copy_from_user(buf, buffer, count)) { 262 ret = -EFAULT; 263 goto out; 264 } 265 buf[count] = '\0'; 266 sym = strstrip(buf); 267 268 mutex_lock(&fei_lock); 269 270 /* Writing just spaces will remove all injection points */ 271 if (sym[0] == '\0') { 272 fei_attr_remove_all(); 273 ret = count; 274 goto out; 275 } 276 /* Writing !function will remove one injection point */ 277 if (sym[0] == '!') { 278 attr = fei_attr_lookup(sym + 1); 279 if (!attr) { 280 ret = -ENOENT; 281 goto out; 282 } 283 fei_attr_remove(attr); 284 ret = count; 285 goto out; 286 } 287 288 addr = kallsyms_lookup_name(sym); 289 if (!addr) { 290 ret = -EINVAL; 291 goto out; 292 } 293 if (!within_error_injection_list(addr)) { 294 ret = -ERANGE; 295 goto out; 296 } 297 if (fei_attr_lookup(sym)) { 298 ret = -EBUSY; 299 goto out; 300 } 301 attr = fei_attr_new(sym, addr); 302 if (!attr) { 303 ret = -ENOMEM; 304 goto out; 305 } 306 307 ret = register_kprobe(&attr->kp); 308 if (!ret) 309 ret = fei_debugfs_add_attr(attr); 310 if (ret < 0) 311 fei_attr_remove(attr); 312 else { 313 list_add_tail(&attr->list, &fei_attr_list); 314 ret = count; 315 } 316 out: 317 kfree(buf); 318 mutex_unlock(&fei_lock); 319 return ret; 320 } 321 322 static const struct file_operations fei_ops = { 323 .open = fei_open, 324 .read = seq_read, 325 .write = fei_write, 326 .llseek = seq_lseek, 327 .release = seq_release, 328 }; 329 330 static int __init fei_debugfs_init(void) 331 { 332 struct dentry *dir; 333 334 dir = fault_create_debugfs_attr("fail_function", NULL, 335 &fei_fault_attr); 336 if (IS_ERR(dir)) 337 return PTR_ERR(dir); 338 339 /* injectable attribute is just a symlink of error_inject/list */ 340 if (!debugfs_create_symlink("injectable", dir, 341 "../error_injection/list")) 342 goto error; 343 344 if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops)) 345 goto error; 346 347 fei_debugfs_dir = dir; 348 349 return 0; 350 error: 351 debugfs_remove_recursive(dir); 352 return -ENOMEM; 353 } 354 355 late_initcall(fei_debugfs_init); 356