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->no_warn)
45 		return;
46 
47 	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
48 		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
49 		       "name %pd, interval %lu, probability %lu, "
50 		       "space %d, times %d\n", attr->dname,
51 		       attr->interval, attr->probability,
52 		       atomic_read(&attr->space),
53 		       atomic_read(&attr->times));
54 		if (attr->verbose > 1)
55 			dump_stack();
56 	}
57 }
58 
59 #define atomic_dec_not_zero(v)		atomic_add_unless((v), -1, 0)
60 
fail_task(struct fault_attr * attr,struct task_struct * task)61 static bool fail_task(struct fault_attr *attr, struct task_struct *task)
62 {
63 	return in_task() && task->make_it_fail;
64 }
65 
66 #define MAX_STACK_TRACE_DEPTH 32
67 
68 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
69 
fail_stacktrace(struct fault_attr * attr)70 static bool fail_stacktrace(struct fault_attr *attr)
71 {
72 	int depth = attr->stacktrace_depth;
73 	unsigned long entries[MAX_STACK_TRACE_DEPTH];
74 	int n, nr_entries;
75 	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
76 
77 	if (depth == 0)
78 		return found;
79 
80 	nr_entries = stack_trace_save(entries, depth, 1);
81 	for (n = 0; n < nr_entries; n++) {
82 		if (attr->reject_start <= entries[n] &&
83 			       entries[n] < attr->reject_end)
84 			return false;
85 		if (attr->require_start <= entries[n] &&
86 			       entries[n] < attr->require_end)
87 			found = true;
88 	}
89 	return found;
90 }
91 
92 #else
93 
fail_stacktrace(struct fault_attr * attr)94 static inline bool fail_stacktrace(struct fault_attr *attr)
95 {
96 	return true;
97 }
98 
99 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
100 
101 /*
102  * This code is stolen from failmalloc-1.0
103  * http://www.nongnu.org/failmalloc/
104  */
105 
should_fail(struct fault_attr * attr,ssize_t size)106 bool should_fail(struct fault_attr *attr, ssize_t size)
107 {
108 	if (in_task()) {
109 		unsigned int fail_nth = READ_ONCE(current->fail_nth);
110 
111 		if (fail_nth) {
112 			fail_nth--;
113 			WRITE_ONCE(current->fail_nth, fail_nth);
114 			if (!fail_nth)
115 				goto fail;
116 
117 			return false;
118 		}
119 	}
120 
121 	/* No need to check any other properties if the probability is 0 */
122 	if (attr->probability == 0)
123 		return false;
124 
125 	if (attr->task_filter && !fail_task(attr, current))
126 		return false;
127 
128 	if (atomic_read(&attr->times) == 0)
129 		return false;
130 
131 	if (atomic_read(&attr->space) > size) {
132 		atomic_sub(size, &attr->space);
133 		return false;
134 	}
135 
136 	if (attr->interval > 1) {
137 		attr->count++;
138 		if (attr->count % attr->interval)
139 			return false;
140 	}
141 
142 	if (attr->probability <= prandom_u32() % 100)
143 		return false;
144 
145 	if (!fail_stacktrace(attr))
146 		return false;
147 
148 fail:
149 	fail_dump(attr);
150 
151 	if (atomic_read(&attr->times) != -1)
152 		atomic_dec_not_zero(&attr->times);
153 
154 	return true;
155 }
156 EXPORT_SYMBOL_GPL(should_fail);
157 
158 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
159 
debugfs_ul_set(void * data,u64 val)160 static int debugfs_ul_set(void *data, u64 val)
161 {
162 	*(unsigned long *)data = val;
163 	return 0;
164 }
165 
debugfs_ul_get(void * data,u64 * val)166 static int debugfs_ul_get(void *data, u64 *val)
167 {
168 	*val = *(unsigned long *)data;
169 	return 0;
170 }
171 
172 DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
173 
debugfs_create_ul(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)174 static void debugfs_create_ul(const char *name, umode_t mode,
175 			      struct dentry *parent, unsigned long *value)
176 {
177 	debugfs_create_file(name, mode, parent, value, &fops_ul);
178 }
179 
180 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
181 
debugfs_stacktrace_depth_set(void * data,u64 val)182 static int debugfs_stacktrace_depth_set(void *data, u64 val)
183 {
184 	*(unsigned long *)data =
185 		min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
186 
187 	return 0;
188 }
189 
190 DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
191 			debugfs_stacktrace_depth_set, "%llu\n");
192 
debugfs_create_stacktrace_depth(const char * name,umode_t mode,struct dentry * parent,unsigned long * value)193 static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
194 					    struct dentry *parent,
195 					    unsigned long *value)
196 {
197 	debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
198 }
199 
200 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
201 
fault_create_debugfs_attr(const char * name,struct dentry * parent,struct fault_attr * attr)202 struct dentry *fault_create_debugfs_attr(const char *name,
203 			struct dentry *parent, struct fault_attr *attr)
204 {
205 	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
206 	struct dentry *dir;
207 
208 	dir = debugfs_create_dir(name, parent);
209 	if (IS_ERR(dir))
210 		return dir;
211 
212 	debugfs_create_ul("probability", mode, dir, &attr->probability);
213 	debugfs_create_ul("interval", mode, dir, &attr->interval);
214 	debugfs_create_atomic_t("times", mode, dir, &attr->times);
215 	debugfs_create_atomic_t("space", mode, dir, &attr->space);
216 	debugfs_create_ul("verbose", mode, dir, &attr->verbose);
217 	debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
218 			   &attr->ratelimit_state.interval);
219 	debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
220 			   &attr->ratelimit_state.burst);
221 	debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
222 
223 #ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
224 	debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
225 					&attr->stacktrace_depth);
226 	debugfs_create_ul("require-start", mode, dir, &attr->require_start);
227 	debugfs_create_ul("require-end", mode, dir, &attr->require_end);
228 	debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);
229 	debugfs_create_ul("reject-end", mode, dir, &attr->reject_end);
230 #endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
231 
232 	attr->dname = dget(dir);
233 	return dir;
234 }
235 EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
236 
237 #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
238