add infrastructure for tagging functions as error injectable

Using BPF we can override kprob'ed functions and return arbitrary
values.  Obviously this can be a bit unsafe, so make this feature opt-in
for functions.  Simply tag a function with KPROBE_ERROR_INJECT_SYMBOL in
order to give BPF access to that function for error injection purposes.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Josef Bacik 2017-12-11 11:36:46 -05:00 committed by Alexei Starovoitov
parent a23967c181
commit 92ace9991d
6 changed files with 195 additions and 1 deletions

View File

@ -136,6 +136,15 @@
#define KPROBE_BLACKLIST()
#endif
#ifdef CONFIG_BPF_KPROBE_OVERRIDE
#define ERROR_INJECT_LIST() . = ALIGN(8); \
VMLINUX_SYMBOL(__start_kprobe_error_inject_list) = .; \
KEEP(*(_kprobe_error_inject_list)) \
VMLINUX_SYMBOL(__stop_kprobe_error_inject_list) = .;
#else
#define ERROR_INJECT_LIST()
#endif
#ifdef CONFIG_EVENT_TRACING
#define FTRACE_EVENTS() . = ALIGN(8); \
VMLINUX_SYMBOL(__start_ftrace_events) = .; \
@ -564,6 +573,7 @@
FTRACE_EVENTS() \
TRACE_SYSCALLS() \
KPROBE_BLACKLIST() \
ERROR_INJECT_LIST() \
MEM_DISCARD(init.rodata) \
CLK_OF_TABLES() \
RESERVEDMEM_OF_TABLES() \

View File

@ -580,4 +580,15 @@ extern const struct bpf_func_proto bpf_sock_map_update_proto;
void bpf_user_rnd_init_once(void);
u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
#ifdef CONFIG_BPF_KPROBE_OVERRIDE
#define BPF_ALLOW_ERROR_INJECTION(fname) \
static unsigned long __used \
__attribute__((__section__("_kprobe_error_inject_list"))) \
_eil_addr_##fname = (unsigned long)fname;
#else
#define BPF_ALLOW_ERROR_INJECTION(fname)
#endif
#endif
#endif /* _LINUX_BPF_H */

View File

@ -271,6 +271,7 @@ extern bool arch_kprobe_on_func_entry(unsigned long offset);
extern bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset);
extern bool within_kprobe_blacklist(unsigned long addr);
extern bool within_kprobe_error_injection_list(unsigned long addr);
struct kprobe_insn_cache {
struct mutex mutex;

View File

@ -475,6 +475,11 @@ struct module {
ctor_fn_t *ctors;
unsigned int num_ctors;
#endif
#ifdef CONFIG_BPF_KPROBE_OVERRIDE
unsigned int num_kprobe_ei_funcs;
unsigned long *kprobe_ei_funcs;
#endif
} ____cacheline_aligned __randomize_layout;
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}

View File

@ -83,6 +83,16 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
return &(kretprobe_table_locks[hash].lock);
}
/* List of symbols that can be overriden for error injection. */
static LIST_HEAD(kprobe_error_injection_list);
static DEFINE_MUTEX(kprobe_ei_mutex);
struct kprobe_ei_entry {
struct list_head list;
unsigned long start_addr;
unsigned long end_addr;
void *priv;
};
/* Blacklist -- list of struct kprobe_blacklist_entry */
static LIST_HEAD(kprobe_blacklist);
@ -1394,6 +1404,17 @@ bool within_kprobe_blacklist(unsigned long addr)
return false;
}
bool within_kprobe_error_injection_list(unsigned long addr)
{
struct kprobe_ei_entry *ent;
list_for_each_entry(ent, &kprobe_error_injection_list, list) {
if (addr >= ent->start_addr && addr < ent->end_addr)
return true;
}
return false;
}
/*
* If we have a symbol_name argument, look it up and add the offset field
* to it. This way, we can specify a relative address to a symbol.
@ -2168,6 +2189,86 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
return 0;
}
#ifdef CONFIG_BPF_KPROBE_OVERRIDE
/* Markers of the _kprobe_error_inject_list section */
extern unsigned long __start_kprobe_error_inject_list[];
extern unsigned long __stop_kprobe_error_inject_list[];
/*
* Lookup and populate the kprobe_error_injection_list.
*
* For safety reasons we only allow certain functions to be overriden with
* bpf_error_injection, so we need to populate the list of the symbols that have
* been marked as safe for overriding.
*/
static void populate_kprobe_error_injection_list(unsigned long *start,
unsigned long *end,
void *priv)
{
unsigned long *iter;
struct kprobe_ei_entry *ent;
unsigned long entry, offset = 0, size = 0;
mutex_lock(&kprobe_ei_mutex);
for (iter = start; iter < end; iter++) {
entry = arch_deref_entry_point((void *)*iter);
if (!kernel_text_address(entry) ||
!kallsyms_lookup_size_offset(entry, &size, &offset)) {
pr_err("Failed to find error inject entry at %p\n",
(void *)entry);
continue;
}
ent = kmalloc(sizeof(*ent), GFP_KERNEL);
if (!ent)
break;
ent->start_addr = entry;
ent->end_addr = entry + size;
ent->priv = priv;
INIT_LIST_HEAD(&ent->list);
list_add_tail(&ent->list, &kprobe_error_injection_list);
}
mutex_unlock(&kprobe_ei_mutex);
}
static void __init populate_kernel_kprobe_ei_list(void)
{
populate_kprobe_error_injection_list(__start_kprobe_error_inject_list,
__stop_kprobe_error_inject_list,
NULL);
}
static void module_load_kprobe_ei_list(struct module *mod)
{
if (!mod->num_kprobe_ei_funcs)
return;
populate_kprobe_error_injection_list(mod->kprobe_ei_funcs,
mod->kprobe_ei_funcs +
mod->num_kprobe_ei_funcs, mod);
}
static void module_unload_kprobe_ei_list(struct module *mod)
{
struct kprobe_ei_entry *ent, *n;
if (!mod->num_kprobe_ei_funcs)
return;
mutex_lock(&kprobe_ei_mutex);
list_for_each_entry_safe(ent, n, &kprobe_error_injection_list, list) {
if (ent->priv == mod) {
list_del_init(&ent->list);
kfree(ent);
}
}
mutex_unlock(&kprobe_ei_mutex);
}
#else
static inline void __init populate_kernel_kprobe_ei_list(void) {}
static inline void module_load_kprobe_ei_list(struct module *m) {}
static inline void module_unload_kprobe_ei_list(struct module *m) {}
#endif
/* Module notifier call back, checking kprobes on the module */
static int kprobes_module_callback(struct notifier_block *nb,
unsigned long val, void *data)
@ -2178,6 +2279,11 @@ static int kprobes_module_callback(struct notifier_block *nb,
unsigned int i;
int checkcore = (val == MODULE_STATE_GOING);
if (val == MODULE_STATE_COMING)
module_load_kprobe_ei_list(mod);
else if (val == MODULE_STATE_GOING)
module_unload_kprobe_ei_list(mod);
if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
return NOTIFY_DONE;
@ -2240,6 +2346,8 @@ static int __init init_kprobes(void)
pr_err("Please take care of using kprobes.\n");
}
populate_kernel_kprobe_ei_list();
if (kretprobe_blacklist_size) {
/* lookup the function address from its name */
for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
@ -2407,6 +2515,56 @@ static const struct file_operations debugfs_kprobe_blacklist_ops = {
.release = seq_release,
};
/*
* kprobes/error_injection_list -- shows which functions can be overriden for
* error injection.
* */
static void *kprobe_ei_seq_start(struct seq_file *m, loff_t *pos)
{
mutex_lock(&kprobe_ei_mutex);
return seq_list_start(&kprobe_error_injection_list, *pos);
}
static void kprobe_ei_seq_stop(struct seq_file *m, void *v)
{
mutex_unlock(&kprobe_ei_mutex);
}
static void *kprobe_ei_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
return seq_list_next(v, &kprobe_error_injection_list, pos);
}
static int kprobe_ei_seq_show(struct seq_file *m, void *v)
{
char buffer[KSYM_SYMBOL_LEN];
struct kprobe_ei_entry *ent =
list_entry(v, struct kprobe_ei_entry, list);
sprint_symbol(buffer, ent->start_addr);
seq_printf(m, "%s\n", buffer);
return 0;
}
static const struct seq_operations kprobe_ei_seq_ops = {
.start = kprobe_ei_seq_start,
.next = kprobe_ei_seq_next,
.stop = kprobe_ei_seq_stop,
.show = kprobe_ei_seq_show,
};
static int kprobe_ei_open(struct inode *inode, struct file *filp)
{
return seq_open(filp, &kprobe_ei_seq_ops);
}
static const struct file_operations debugfs_kprobe_ei_ops = {
.open = kprobe_ei_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
static void arm_all_kprobes(void)
{
struct hlist_head *head;
@ -2548,6 +2706,11 @@ static int __init debugfs_kprobe_init(void)
if (!file)
goto error;
file = debugfs_create_file("error_injection_list", 0444, dir, NULL,
&debugfs_kprobe_ei_ops);
if (!file)
goto error;
return 0;
error:

View File

@ -3118,7 +3118,11 @@ static int find_module_sections(struct module *mod, struct load_info *info)
sizeof(*mod->ftrace_callsites),
&mod->num_ftrace_callsites);
#endif
#ifdef CONFIG_BPF_KPROBE_OVERRIDE
mod->kprobe_ei_funcs = section_objs(info, "_kprobe_error_inject_list",
sizeof(*mod->kprobe_ei_funcs),
&mod->num_kprobe_ei_funcs);
#endif
mod->extable = section_objs(info, "__ex_table",
sizeof(*mod->extable), &mod->num_exentries);