1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/kernel.h>
3 #include <linux/init.h>
4 #include <linux/random.h>
5 #include <linux/sched.h>
6 #include <linux/stat.h>
7 #include <linux/types.h>
8 #include <linux/fs.h>
9 #include <linux/export.h>
10 #include <linux/interrupt.h>
11 #include <linux/stacktrace.h>
12 #include <linux/fault-inject.h>
13 
14 /*
15  * setup_fault_attr() is a helper function for various __setup handlers, so it
16  * returns 0 on error, because that is what __setup handlers do.
17  */
setup_fault_attr(struct fault_attr * attr,char * str)18 int setup_fault_attr(struct fault_attr *attr, char *str)
19 {
20 	unsigned long probability;
21 	unsigned long interval;
22 	int times;
23 	int space;
24 
25 	/* "<interval>,<probability>,<space>,<times>" */
26 	if (sscanf(str, "%lu,%lu,%d,%d",
27 			&interval, &probability, &space, &times) < 4) {
28 		printk(KERN_WARNING
29 			"FAULT_INJECTION: failed to parse arguments\n");
30 		return 0;
31 	}
32 
33 	attr->probability = probability;
34 	attr->interval = interval;
35 	atomic_set(&attr->times, times);
36 	atomic_set(&attr->space, space);
37 
38 	return 1;
39 }
40 EXPORT_SYMBOL_GPL(setup_fault_attr);
41 
fail_dump(struct fault_attr * attr)42 static void fail_dump(struct fault_attr *attr)
43 {
44 	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
45 		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
46 		       "name %pd, interval %lu, probability %lu, "
47 		       "space %d, times %d\n", attr->dname,
48 		       attr->interval, attr->probability,
49 		       atomic_read(&attr->space),
50 		       atomic_read(&attr->times));
51 		if (attr->verbose > 1)
52 			dump_stack();
53 	}
54 }
55 
56 #define atomic_dec_not_zero(v)		atomic_add_unless((v), -1, 0)
57 
fail_task(struct fault_attr * attr,struct task_struct * task)58 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
59 {
60 	return in_task() && task->make_it_fail;
61 }
62 
63 #define MAX_STACK_TRACE_DEPTH 32
64 
65 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
66 
fail_stacktrace(struct fault_attr * attr)67 static bool fail_stacktrace(struct fault_attr *attr)
68 {
69 	int depth = attr->stacktrace_depth;
70 	unsigned long entries[MAX_STACK_TRACE_DEPTH];
71 	int n, nr_entries;
72 	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
73 
74 	if (depth == 0 || (found && !attr->reject_start && !attr->reject_end))
75 		return found;
76 
77 	nr_entries = stack_trace_save(entries, depth, 1);
78 	for (n = 0; n < nr_entries; n++) {
79 		if (attr->reject_start <= entries[n] &&
80 			       entries[n] < attr->reject_end)
81 			return false;
82 		if (attr->require_start <= entries[n] &&
83 			       entries[n] < attr->require_end)
84 			found = true;
85 	}
86 	return found;
87 }
88 
89 #else
90 
fail_stacktrace(struct fault_attr * attr)91 static inline bool fail_stacktrace(struct fault_attr *attr)
92 {
93 	return true;
94 }
95 
96 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
97 
98 /*
99  * This code is stolen from failmalloc-1.0
100  * http://www.nongnu.org/failmalloc/
101  */
102 
should_fail_ex(struct fault_attr * attr,ssize_t size,int flags)103 bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
104 {
105 	bool stack_checked = false;
106 
107 	if (in_task()) {
108 		unsigned int fail_nth = READ_ONCE(current->fail_nth);
109 
110 		if (fail_nth) {
111 			if (!fail_stacktrace(attr))
112 				return false;
113 
114 			stack_checked = true;
115 			fail_nth--;
116 			WRITE_ONCE(current->fail_nth, fail_nth);
117 			if (!fail_nth)
118 				goto fail;
119 
120 			return false;
121 		}
122 	}
123 
124 	/* No need to check any other properties if the probability is 0 */
125 	if (attr->probability == 0)
126 		return false;
127 
128 	if (attr->task_filter && !fail_task(attr, current))
129 		return false;
130 
131 	if (atomic_read(&attr->times) == 0)
132 		return false;
133 
134 	if (!stack_checked && !fail_stacktrace(attr))
135 		return false;
136 
137 	if (atomic_read(&attr->space) > size) {
138 		atomic_sub(size, &attr->space);
139 		return false;
140 	}
141 
142 	if (attr->interval > 1) {
143 		attr->count++;
144 		if (attr->count % attr->interval)
145 			return false;
146 	}
147 
148 	if (attr->probability <= get_random_u32_below(100))
149 		return false;
150 
151 fail:
152 	if (!(flags & FAULT_NOWARN))
153 		fail_dump(attr);
154 
155 	if (atomic_read(&attr->times) != -1)
156 		atomic_dec_not_zero(&attr->times);
157 
158 	return true;
159 }
160 
should_fail(struct fault_attr * attr,ssize_t size)161 bool should_fail(struct fault_attr *attr, ssize_t size)
162 {
163 	return should_fail_ex(attr, size, 0);
164 }
165 EXPORT_SYMBOL_GPL(should_fail);
166 
167 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
168 
debugfs_ul_set(void * data,u64 val)169 static int debugfs_ul_set(void *data, u64 val)
170 {
171 	*(unsigned long *)data = val;
172 	return 0;
173 }
174 
debugfs_ul_get(void * data,u64 * val)175 static int debugfs_ul_get(void *data, u64 *val)
176 {
177 	*val = *(unsigned long *)data;
178 	return 0;
179 }
180 
181 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
182 
debugfs_create_ul(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)183 static void debugfs_create_ul(const char *name, umode_t mode,
184 			      struct dentry *parent, unsigned long *value)
185 {
186 	debugfs_create_file(name, mode, parent, value, &fops_ul);
187 }
188 
189 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
190 
debugfs_stacktrace_depth_set(void * data,u64 val)191 static int debugfs_stacktrace_depth_set(void *data, u64 val)
192 {
193 	*(unsigned long *)data =
194 		min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
195 
196 	return 0;
197 }
198 
199 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
200 			debugfs_stacktrace_depth_set, "%llu\n");
201 
debugfs_create_stacktrace_depth(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)202 static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
203 					    struct dentry *parent,
204 					    unsigned long *value)
205 {
206 	debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
207 }
208 
209 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
210 
fault_create_debugfs_attr(const char * name,struct dentry * parent,struct fault_attr * attr)211 struct dentry *fault_create_debugfs_attr(const char *name,
212 			struct dentry *parent, struct fault_attr *attr)
213 {
214 	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
215 	struct dentry *dir;
216 
217 	dir = debugfs_create_dir(name, parent);
218 	if (IS_ERR(dir))
219 		return dir;
220 
221 	debugfs_create_ul("probability", mode, dir, &attr->probability);
222 	debugfs_create_ul("interval", mode, dir, &attr->interval);
223 	debugfs_create_atomic_t("times", mode, dir, &attr->times);
224 	debugfs_create_atomic_t("space", mode, dir, &attr->space);
225 	debugfs_create_ul("verbose", mode, dir, &attr->verbose);
226 	debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
227 			   &attr->ratelimit_state.interval);
228 	debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
229 			   &attr->ratelimit_state.burst);
230 	debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
231 
232 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
233 	debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
234 					&attr->stacktrace_depth);
235 	debugfs_create_xul("require-start", mode, dir, &attr->require_start);
236 	debugfs_create_xul("require-end", mode, dir, &attr->require_end);
237 	debugfs_create_xul("reject-start", mode, dir, &attr->reject_start);
238 	debugfs_create_xul("reject-end", mode, dir, &attr->reject_end);
239 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
240 
241 	attr->dname = dget(dir);
242 	return dir;
243 }
244 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
245 
246 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
247