linux/kernel/fail_function.c
Greg Kroah-Hartman 4aa3b1f67d fail_function: no need to check return value of debugfs_create functions
When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Cc: Kees Cook <keescook@chromium.org>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: zhong jiang <zhongjiang@huawei.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-03 15:49:06 +02:00

343 lines
6.9 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* fail_function.c: Function-based error injection
*/
#include <linux/error-injection.h>
#include <linux/debugfs.h>
#include <linux/fault-inject.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
unsigned long flags)
{
/*
* A dummy post handler is required to prohibit optimizing, because
* jump optimization does not support execution path overriding.
*/
}
struct fei_attr {
struct list_head list;
struct kprobe kp;
unsigned long retval;
};
static DEFINE_MUTEX(fei_lock);
static LIST_HEAD(fei_attr_list);
static DECLARE_FAULT_ATTR(fei_fault_attr);
static struct dentry *fei_debugfs_dir;
static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
{
switch (get_injectable_error_type(addr)) {
case EI_ETYPE_NULL:
if (retv != 0)
return 0;
break;
case EI_ETYPE_ERRNO:
if (retv < (unsigned long)-MAX_ERRNO)
return (unsigned long)-EINVAL;
break;
case EI_ETYPE_ERRNO_NULL:
if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
return (unsigned long)-EINVAL;
break;
}
return retv;
}
static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
{
struct fei_attr *attr;
attr = kzalloc(sizeof(*attr), GFP_KERNEL);
if (attr) {
attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
if (!attr->kp.symbol_name) {
kfree(attr);
return NULL;
}
attr->kp.pre_handler = fei_kprobe_handler;
attr->kp.post_handler = fei_post_handler;
attr->retval = adjust_error_retval(addr, 0);
INIT_LIST_HEAD(&attr->list);
}
return attr;
}
static void fei_attr_free(struct fei_attr *attr)
{
if (attr) {
kfree(attr->kp.symbol_name);
kfree(attr);
}
}
static struct fei_attr *fei_attr_lookup(const char *sym)
{
struct fei_attr *attr;
list_for_each_entry(attr, &fei_attr_list, list) {
if (!strcmp(attr->kp.symbol_name, sym))
return attr;
}
return NULL;
}
static bool fei_attr_is_valid(struct fei_attr *_attr)
{
struct fei_attr *attr;
list_for_each_entry(attr, &fei_attr_list, list) {
if (attr == _attr)
return true;
}
return false;
}
static int fei_retval_set(void *data, u64 val)
{
struct fei_attr *attr = data;
unsigned long retv = (unsigned long)val;
int err = 0;
mutex_lock(&fei_lock);
/*
* Since this operation can be done after retval file is removed,
* It is safer to check the attr is still valid before accessing
* its member.
*/
if (!fei_attr_is_valid(attr)) {
err = -ENOENT;
goto out;
}
if (attr->kp.addr) {
if (adjust_error_retval((unsigned long)attr->kp.addr,
val) != retv)
err = -EINVAL;
}
if (!err)
attr->retval = val;
out:
mutex_unlock(&fei_lock);
return err;
}
static int fei_retval_get(void *data, u64 *val)
{
struct fei_attr *attr = data;
int err = 0;
mutex_lock(&fei_lock);
/* Here we also validate @attr to ensure it still exists. */
if (!fei_attr_is_valid(attr))
err = -ENOENT;
else
*val = attr->retval;
mutex_unlock(&fei_lock);
return err;
}
DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
"%llx\n");
static void fei_debugfs_add_attr(struct fei_attr *attr)
{
struct dentry *dir;
dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops);
}
static void fei_debugfs_remove_attr(struct fei_attr *attr)
{
struct dentry *dir;
dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
debugfs_remove_recursive(dir);
}
static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
{
struct fei_attr *attr = container_of(kp, struct fei_attr, kp);
if (should_fail(&fei_fault_attr, 1)) {
regs_set_return_value(regs, attr->retval);
override_function_with_return(regs);
return 1;
}
return 0;
}
NOKPROBE_SYMBOL(fei_kprobe_handler)
static void *fei_seq_start(struct seq_file *m, loff_t *pos)
{
mutex_lock(&fei_lock);
return seq_list_start(&fei_attr_list, *pos);
}
static void fei_seq_stop(struct seq_file *m, void *v)
{
mutex_unlock(&fei_lock);
}
static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
return seq_list_next(v, &fei_attr_list, pos);
}
static int fei_seq_show(struct seq_file *m, void *v)
{
struct fei_attr *attr = list_entry(v, struct fei_attr, list);
seq_printf(m, "%ps\n", attr->kp.addr);
return 0;
}
static const struct seq_operations fei_seq_ops = {
.start = fei_seq_start,
.next = fei_seq_next,
.stop = fei_seq_stop,
.show = fei_seq_show,
};
static int fei_open(struct inode *inode, struct file *file)
{
return seq_open(file, &fei_seq_ops);
}
static void fei_attr_remove(struct fei_attr *attr)
{
fei_debugfs_remove_attr(attr);
unregister_kprobe(&attr->kp);
list_del(&attr->list);
fei_attr_free(attr);
}
static void fei_attr_remove_all(void)
{
struct fei_attr *attr, *n;
list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
fei_attr_remove(attr);
}
}
static ssize_t fei_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct fei_attr *attr;
unsigned long addr;
char *buf, *sym;
int ret;
/* cut off if it is too long */
if (count > KSYM_NAME_LEN)
count = KSYM_NAME_LEN;
buf = kmalloc(count + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
if (copy_from_user(buf, buffer, count)) {
ret = -EFAULT;
goto out;
}
buf[count] = '\0';
sym = strstrip(buf);
mutex_lock(&fei_lock);
/* Writing just spaces will remove all injection points */
if (sym[0] == '\0') {
fei_attr_remove_all();
ret = count;
goto out;
}
/* Writing !function will remove one injection point */
if (sym[0] == '!') {
attr = fei_attr_lookup(sym + 1);
if (!attr) {
ret = -ENOENT;
goto out;
}
fei_attr_remove(attr);
ret = count;
goto out;
}
addr = kallsyms_lookup_name(sym);
if (!addr) {
ret = -EINVAL;
goto out;
}
if (!within_error_injection_list(addr)) {
ret = -ERANGE;
goto out;
}
if (fei_attr_lookup(sym)) {
ret = -EBUSY;
goto out;
}
attr = fei_attr_new(sym, addr);
if (!attr) {
ret = -ENOMEM;
goto out;
}
ret = register_kprobe(&attr->kp);
if (!ret)
fei_debugfs_add_attr(attr);
if (ret < 0)
fei_attr_remove(attr);
else {
list_add_tail(&attr->list, &fei_attr_list);
ret = count;
}
out:
kfree(buf);
mutex_unlock(&fei_lock);
return ret;
}
static const struct file_operations fei_ops = {
.open = fei_open,
.read = seq_read,
.write = fei_write,
.llseek = seq_lseek,
.release = seq_release,
};
static int __init fei_debugfs_init(void)
{
struct dentry *dir;
dir = fault_create_debugfs_attr("fail_function", NULL,
&fei_fault_attr);
if (IS_ERR(dir))
return PTR_ERR(dir);
/* injectable attribute is just a symlink of error_inject/list */
debugfs_create_symlink("injectable", dir, "../error_injection/list");
debugfs_create_file("inject", 0600, dir, NULL, &fei_ops);
fei_debugfs_dir = dir;
return 0;
}
late_initcall(fei_debugfs_init);