linux/lib/fault-inject.c
Jason A. Donenfeld 81895a65ec treewide: use prandom_u32_max() when possible, part 1
Rather than incurring a division or requesting too many random bytes for
the given range, use the prandom_u32_max() function, which only takes
the minimum required bytes from the RNG and avoids divisions. This was
done mechanically with this coccinelle script:

@basic@
expression E;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u64;
@@
(
- ((T)get_random_u32() % (E))
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ((E) - 1))
+ prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2)
|
- ((u64)(E) * get_random_u32() >> 32)
+ prandom_u32_max(E)
|
- ((T)get_random_u32() & ~PAGE_MASK)
+ prandom_u32_max(PAGE_SIZE)
)

@multi_line@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
identifier RAND;
expression E;
@@

-       RAND = get_random_u32();
        ... when != RAND
-       RAND %= (E);
+       RAND = prandom_u32_max(E);

// Find a potential literal
@literal_mask@
expression LITERAL;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
position p;
@@

        ((T)get_random_u32()@p & (LITERAL))

// Add one to the literal.
@script:python add_one@
literal << literal_mask.LITERAL;
RESULT;
@@

value = None
if literal.startswith('0x'):
        value = int(literal, 16)
elif literal[0] in '123456789':
        value = int(literal, 10)
if value is None:
        print("I don't know how to handle %s" % (literal))
        cocci.include_match(False)
elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1:
        print("Skipping 0x%x for cleanup elsewhere" % (value))
        cocci.include_match(False)
elif value & (value + 1) != 0:
        print("Skipping 0x%x because it's not a power of two minus one" % (value))
        cocci.include_match(False)
elif literal.startswith('0x'):
        coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1))
else:
        coccinelle.RESULT = cocci.make_expr("%d" % (value + 1))

// Replace the literal mask with the calculated result.
@plus_one@
expression literal_mask.LITERAL;
position literal_mask.p;
expression add_one.RESULT;
identifier FUNC;
@@

-       (FUNC()@p & (LITERAL))
+       prandom_u32_max(RESULT)

@collapse_ret@
type T;
identifier VAR;
expression E;
@@

 {
-       T VAR;
-       VAR = (E);
-       return VAR;
+       return E;
 }

@drop_var@
type T;
identifier VAR;
@@

 {
-       T VAR;
        ... when != VAR
 }

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: KP Singh <kpsingh@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 and sbitmap
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> # for drbd
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc
Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-10-11 17:42:55 -06:00

238 lines
5.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/stacktrace.h>
#include <linux/fault-inject.h>
/*
* setup_fault_attr() is a helper function for various __setup handlers, so it
* returns 0 on error, because that is what __setup handlers do.
*/
int setup_fault_attr(struct fault_attr *attr, char *str)
{
unsigned long probability;
unsigned long interval;
int times;
int space;
/* "<interval>,<probability>,<space>,<times>" */
if (sscanf(str, "%lu,%lu,%d,%d",
&interval, &probability, &space, &times) < 4) {
printk(KERN_WARNING
"FAULT_INJECTION: failed to parse arguments\n");
return 0;
}
attr->probability = probability;
attr->interval = interval;
atomic_set(&attr->times, times);
atomic_set(&attr->space, space);
return 1;
}
EXPORT_SYMBOL_GPL(setup_fault_attr);
static void fail_dump(struct fault_attr *attr)
{
if (attr->no_warn)
return;
if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
"name %pd, interval %lu, probability %lu, "
"space %d, times %d\n", attr->dname,
attr->interval, attr->probability,
atomic_read(&attr->space),
atomic_read(&attr->times));
if (attr->verbose > 1)
dump_stack();
}
}
#define atomic_dec_not_zero(v) atomic_add_unless((v), -1, 0)
static bool fail_task(struct fault_attr *attr, struct task_struct *task)
{
return in_task() && task->make_it_fail;
}
#define MAX_STACK_TRACE_DEPTH 32
#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
static bool fail_stacktrace(struct fault_attr *attr)
{
int depth = attr->stacktrace_depth;
unsigned long entries[MAX_STACK_TRACE_DEPTH];
int n, nr_entries;
bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
if (depth == 0)
return found;
nr_entries = stack_trace_save(entries, depth, 1);
for (n = 0; n < nr_entries; n++) {
if (attr->reject_start <= entries[n] &&
entries[n] < attr->reject_end)
return false;
if (attr->require_start <= entries[n] &&
entries[n] < attr->require_end)
found = true;
}
return found;
}
#else
static inline bool fail_stacktrace(struct fault_attr *attr)
{
return true;
}
#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
/*
* This code is stolen from failmalloc-1.0
* http://www.nongnu.org/failmalloc/
*/
bool should_fail(struct fault_attr *attr, ssize_t size)
{
if (in_task()) {
unsigned int fail_nth = READ_ONCE(current->fail_nth);
if (fail_nth) {
fail_nth--;
WRITE_ONCE(current->fail_nth, fail_nth);
if (!fail_nth)
goto fail;
return false;
}
}
/* No need to check any other properties if the probability is 0 */
if (attr->probability == 0)
return false;
if (attr->task_filter && !fail_task(attr, current))
return false;
if (atomic_read(&attr->times) == 0)
return false;
if (atomic_read(&attr->space) > size) {
atomic_sub(size, &attr->space);
return false;
}
if (attr->interval > 1) {
attr->count++;
if (attr->count % attr->interval)
return false;
}
if (attr->probability <= prandom_u32_max(100))
return false;
if (!fail_stacktrace(attr))
return false;
fail:
fail_dump(attr);
if (atomic_read(&attr->times) != -1)
atomic_dec_not_zero(&attr->times);
return true;
}
EXPORT_SYMBOL_GPL(should_fail);
#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
static int debugfs_ul_set(void *data, u64 val)
{
*(unsigned long *)data = val;
return 0;
}
static int debugfs_ul_get(void *data, u64 *val)
{
*val = *(unsigned long *)data;
return 0;
}
DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
static void debugfs_create_ul(const char *name, umode_t mode,
struct dentry *parent, unsigned long *value)
{
debugfs_create_file(name, mode, parent, value, &fops_ul);
}
#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
static int debugfs_stacktrace_depth_set(void *data, u64 val)
{
*(unsigned long *)data =
min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
return 0;
}
DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
debugfs_stacktrace_depth_set, "%llu\n");
static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
struct dentry *parent,
unsigned long *value)
{
debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
}
#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
struct dentry *fault_create_debugfs_attr(const char *name,
struct dentry *parent, struct fault_attr *attr)
{
umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
struct dentry *dir;
dir = debugfs_create_dir(name, parent);
if (IS_ERR(dir))
return dir;
debugfs_create_ul("probability", mode, dir, &attr->probability);
debugfs_create_ul("interval", mode, dir, &attr->interval);
debugfs_create_atomic_t("times", mode, dir, &attr->times);
debugfs_create_atomic_t("space", mode, dir, &attr->space);
debugfs_create_ul("verbose", mode, dir, &attr->verbose);
debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
&attr->ratelimit_state.interval);
debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
&attr->ratelimit_state.burst);
debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
&attr->stacktrace_depth);
debugfs_create_ul("require-start", mode, dir, &attr->require_start);
debugfs_create_ul("require-end", mode, dir, &attr->require_end);
debugfs_create_ul("reject-start", mode, dir, &attr->reject_start);
debugfs_create_ul("reject-end", mode, dir, &attr->reject_end);
#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
attr->dname = dget(dir);
return dir;
}
EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */