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 if (dir) 177 debugfs_remove_recursive(dir); 178 } 179 180 static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs) 181 { 182 struct fei_attr *attr = container_of(kp, struct fei_attr, kp); 183 184 if (should_fail(&fei_fault_attr, 1)) { 185 regs_set_return_value(regs, attr->retval); 186 override_function_with_return(regs); 187 /* Kprobe specific fixup */ 188 reset_current_kprobe(); 189 preempt_enable_no_resched(); 190 return 1; 191 } 192 193 return 0; 194 } 195 NOKPROBE_SYMBOL(fei_kprobe_handler) 196 197 static void *fei_seq_start(struct seq_file *m, loff_t *pos) 198 { 199 mutex_lock(&fei_lock); 200 return seq_list_start(&fei_attr_list, *pos); 201 } 202 203 static void fei_seq_stop(struct seq_file *m, void *v) 204 { 205 mutex_unlock(&fei_lock); 206 } 207 208 static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos) 209 { 210 return seq_list_next(v, &fei_attr_list, pos); 211 } 212 213 static int fei_seq_show(struct seq_file *m, void *v) 214 { 215 struct fei_attr *attr = list_entry(v, struct fei_attr, list); 216 217 seq_printf(m, "%pf\n", attr->kp.addr); 218 return 0; 219 } 220 221 static const struct seq_operations fei_seq_ops = { 222 .start = fei_seq_start, 223 .next = fei_seq_next, 224 .stop = fei_seq_stop, 225 .show = fei_seq_show, 226 }; 227 228 static int fei_open(struct inode *inode, struct file *file) 229 { 230 return seq_open(file, &fei_seq_ops); 231 } 232 233 static void fei_attr_remove(struct fei_attr *attr) 234 { 235 fei_debugfs_remove_attr(attr); 236 unregister_kprobe(&attr->kp); 237 list_del(&attr->list); 238 fei_attr_free(attr); 239 } 240 241 static void fei_attr_remove_all(void) 242 { 243 struct fei_attr *attr, *n; 244 245 list_for_each_entry_safe(attr, n, &fei_attr_list, list) { 246 fei_attr_remove(attr); 247 } 248 } 249 250 static ssize_t fei_write(struct file *file, const char __user *buffer, 251 size_t count, loff_t *ppos) 252 { 253 struct fei_attr *attr; 254 unsigned long addr; 255 char *buf, *sym; 256 int ret; 257 258 /* cut off if it is too long */ 259 if (count > KSYM_NAME_LEN) 260 count = KSYM_NAME_LEN; 261 buf = kmalloc(count + 1, GFP_KERNEL); 262 if (!buf) 263 return -ENOMEM; 264 265 if (copy_from_user(buf, buffer, count)) { 266 ret = -EFAULT; 267 goto out; 268 } 269 buf[count] = '\0'; 270 sym = strstrip(buf); 271 272 mutex_lock(&fei_lock); 273 274 /* Writing just spaces will remove all injection points */ 275 if (sym[0] == '\0') { 276 fei_attr_remove_all(); 277 ret = count; 278 goto out; 279 } 280 /* Writing !function will remove one injection point */ 281 if (sym[0] == '!') { 282 attr = fei_attr_lookup(sym + 1); 283 if (!attr) { 284 ret = -ENOENT; 285 goto out; 286 } 287 fei_attr_remove(attr); 288 ret = count; 289 goto out; 290 } 291 292 addr = kallsyms_lookup_name(sym); 293 if (!addr) { 294 ret = -EINVAL; 295 goto out; 296 } 297 if (!within_error_injection_list(addr)) { 298 ret = -ERANGE; 299 goto out; 300 } 301 if (fei_attr_lookup(sym)) { 302 ret = -EBUSY; 303 goto out; 304 } 305 attr = fei_attr_new(sym, addr); 306 if (!attr) { 307 ret = -ENOMEM; 308 goto out; 309 } 310 311 ret = register_kprobe(&attr->kp); 312 if (!ret) 313 ret = fei_debugfs_add_attr(attr); 314 if (ret < 0) 315 fei_attr_remove(attr); 316 else { 317 list_add_tail(&attr->list, &fei_attr_list); 318 ret = count; 319 } 320 out: 321 kfree(buf); 322 mutex_unlock(&fei_lock); 323 return ret; 324 } 325 326 static const struct file_operations fei_ops = { 327 .open = fei_open, 328 .read = seq_read, 329 .write = fei_write, 330 .llseek = seq_lseek, 331 .release = seq_release, 332 }; 333 334 static int __init fei_debugfs_init(void) 335 { 336 struct dentry *dir; 337 338 dir = fault_create_debugfs_attr("fail_function", NULL, 339 &fei_fault_attr); 340 if (IS_ERR(dir)) 341 return PTR_ERR(dir); 342 343 /* injectable attribute is just a symlink of error_inject/list */ 344 if (!debugfs_create_symlink("injectable", dir, 345 "../error_injection/list")) 346 goto error; 347 348 if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops)) 349 goto error; 350 351 fei_debugfs_dir = dir; 352 353 return 0; 354 error: 355 debugfs_remove_recursive(dir); 356 return -ENOMEM; 357 } 358 359 late_initcall(fei_debugfs_init); 360