swh:1:snp:173f8deb0c56c557784b4fd217e7608ac6197844
Tip revision: 771c577c23bac90597c685971d7297ea00f99d11 authored by Linus Torvalds on 20 May 2018, 22:31:38 UTC
Linux 4.17-rc6
Linux 4.17-rc6
Tip revision: 771c577
refcount.c
// SPDX-License-Identifier: GPL-2.0
/*
* This is for all the tests related to refcount bugs (e.g. overflow,
* underflow, reaching zero untested, etc).
*/
#include "lkdtm.h"
#include <linux/refcount.h>
#ifdef CONFIG_REFCOUNT_FULL
#define REFCOUNT_MAX (UINT_MAX - 1)
#define REFCOUNT_SATURATED UINT_MAX
#else
#define REFCOUNT_MAX INT_MAX
#define REFCOUNT_SATURATED (INT_MIN / 2)
#endif
static void overflow_check(refcount_t *ref)
{
switch (refcount_read(ref)) {
case REFCOUNT_SATURATED:
pr_info("Overflow detected: saturated\n");
break;
case REFCOUNT_MAX:
pr_warn("Overflow detected: unsafely reset to max\n");
break;
default:
pr_err("Fail: refcount wrapped to %d\n", refcount_read(ref));
}
}
/*
* A refcount_inc() above the maximum value of the refcount implementation,
* should at least saturate, and at most also WARN.
*/
void lkdtm_REFCOUNT_INC_OVERFLOW(void)
{
refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX - 1);
pr_info("attempting good refcount_inc() without overflow\n");
refcount_dec(&over);
refcount_inc(&over);
pr_info("attempting bad refcount_inc() overflow\n");
refcount_inc(&over);
refcount_inc(&over);
overflow_check(&over);
}
/* refcount_add() should behave just like refcount_inc() above. */
void lkdtm_REFCOUNT_ADD_OVERFLOW(void)
{
refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX - 1);
pr_info("attempting good refcount_add() without overflow\n");
refcount_dec(&over);
refcount_dec(&over);
refcount_dec(&over);
refcount_dec(&over);
refcount_add(4, &over);
pr_info("attempting bad refcount_add() overflow\n");
refcount_add(4, &over);
overflow_check(&over);
}
/* refcount_inc_not_zero() should behave just like refcount_inc() above. */
void lkdtm_REFCOUNT_INC_NOT_ZERO_OVERFLOW(void)
{
refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX);
pr_info("attempting bad refcount_inc_not_zero() overflow\n");
if (!refcount_inc_not_zero(&over))
pr_warn("Weird: refcount_inc_not_zero() reported zero\n");
overflow_check(&over);
}
/* refcount_add_not_zero() should behave just like refcount_inc() above. */
void lkdtm_REFCOUNT_ADD_NOT_ZERO_OVERFLOW(void)
{
refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX);
pr_info("attempting bad refcount_add_not_zero() overflow\n");
if (!refcount_add_not_zero(6, &over))
pr_warn("Weird: refcount_add_not_zero() reported zero\n");
overflow_check(&over);
}
static void check_zero(refcount_t *ref)
{
switch (refcount_read(ref)) {
case REFCOUNT_SATURATED:
pr_info("Zero detected: saturated\n");
break;
case REFCOUNT_MAX:
pr_warn("Zero detected: unsafely reset to max\n");
break;
case 0:
pr_warn("Still at zero: refcount_inc/add() must not inc-from-0\n");
break;
default:
pr_err("Fail: refcount went crazy: %d\n", refcount_read(ref));
}
}
/*
* A refcount_dec(), as opposed to a refcount_dec_and_test(), when it hits
* zero it should either saturate (when inc-from-zero isn't protected)
* or stay at zero (when inc-from-zero is protected) and should WARN for both.
*/
void lkdtm_REFCOUNT_DEC_ZERO(void)
{
refcount_t zero = REFCOUNT_INIT(2);
pr_info("attempting good refcount_dec()\n");
refcount_dec(&zero);
pr_info("attempting bad refcount_dec() to zero\n");
refcount_dec(&zero);
check_zero(&zero);
}
static void check_negative(refcount_t *ref, int start)
{
/*
* CONFIG_REFCOUNT_FULL refuses to move a refcount at all on an
* over-sub, so we have to track our starting position instead of
* looking only at zero-pinning.
*/
if (refcount_read(ref) == start) {
pr_warn("Still at %d: refcount_inc/add() must not inc-from-0\n",
start);
return;
}
switch (refcount_read(ref)) {
case REFCOUNT_SATURATED:
pr_info("Negative detected: saturated\n");
break;
case REFCOUNT_MAX:
pr_warn("Negative detected: unsafely reset to max\n");
break;
default:
pr_err("Fail: refcount went crazy: %d\n", refcount_read(ref));
}
}
/* A refcount_dec() going negative should saturate and may WARN. */
void lkdtm_REFCOUNT_DEC_NEGATIVE(void)
{
refcount_t neg = REFCOUNT_INIT(0);
pr_info("attempting bad refcount_dec() below zero\n");
refcount_dec(&neg);
check_negative(&neg, 0);
}
/*
* A refcount_dec_and_test() should act like refcount_dec() above when
* going negative.
*/
void lkdtm_REFCOUNT_DEC_AND_TEST_NEGATIVE(void)
{
refcount_t neg = REFCOUNT_INIT(0);
pr_info("attempting bad refcount_dec_and_test() below zero\n");
if (refcount_dec_and_test(&neg))
pr_warn("Weird: refcount_dec_and_test() reported zero\n");
check_negative(&neg, 0);
}
/*
* A refcount_sub_and_test() should act like refcount_dec_and_test()
* above when going negative.
*/
void lkdtm_REFCOUNT_SUB_AND_TEST_NEGATIVE(void)
{
refcount_t neg = REFCOUNT_INIT(3);
pr_info("attempting bad refcount_sub_and_test() below zero\n");
if (refcount_sub_and_test(5, &neg))
pr_warn("Weird: refcount_sub_and_test() reported zero\n");
check_negative(&neg, 3);
}
static void check_from_zero(refcount_t *ref)
{
switch (refcount_read(ref)) {
case 0:
pr_info("Zero detected: stayed at zero\n");
break;
case REFCOUNT_SATURATED:
pr_info("Zero detected: saturated\n");
break;
case REFCOUNT_MAX:
pr_warn("Zero detected: unsafely reset to max\n");
break;
default:
pr_info("Fail: zero not detected, incremented to %d\n",
refcount_read(ref));
}
}
/*
* A refcount_inc() from zero should pin to zero or saturate and may WARN.
* Only CONFIG_REFCOUNT_FULL provides this protection currently.
*/
void lkdtm_REFCOUNT_INC_ZERO(void)
{
refcount_t zero = REFCOUNT_INIT(0);
pr_info("attempting safe refcount_inc_not_zero() from zero\n");
if (!refcount_inc_not_zero(&zero)) {
pr_info("Good: zero detected\n");
if (refcount_read(&zero) == 0)
pr_info("Correctly stayed at zero\n");
else
pr_err("Fail: refcount went past zero!\n");
} else {
pr_err("Fail: Zero not detected!?\n");
}
pr_info("attempting bad refcount_inc() from zero\n");
refcount_inc(&zero);
check_from_zero(&zero);
}
/*
* A refcount_add() should act like refcount_inc() above when starting
* at zero.
*/
void lkdtm_REFCOUNT_ADD_ZERO(void)
{
refcount_t zero = REFCOUNT_INIT(0);
pr_info("attempting safe refcount_add_not_zero() from zero\n");
if (!refcount_add_not_zero(3, &zero)) {
pr_info("Good: zero detected\n");
if (refcount_read(&zero) == 0)
pr_info("Correctly stayed at zero\n");
else
pr_err("Fail: refcount went past zero\n");
} else {
pr_err("Fail: Zero not detected!?\n");
}
pr_info("attempting bad refcount_add() from zero\n");
refcount_add(3, &zero);
check_from_zero(&zero);
}
static void check_saturated(refcount_t *ref)
{
switch (refcount_read(ref)) {
case REFCOUNT_SATURATED:
pr_info("Saturation detected: still saturated\n");
break;
case REFCOUNT_MAX:
pr_warn("Saturation detected: unsafely reset to max\n");
break;
default:
pr_err("Fail: refcount went crazy: %d\n", refcount_read(ref));
}
}
/*
* A refcount_inc() from a saturated value should at most warn about
* being saturated already.
*/
void lkdtm_REFCOUNT_INC_SATURATED(void)
{
refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
pr_info("attempting bad refcount_inc() from saturated\n");
refcount_inc(&sat);
check_saturated(&sat);
}
/* Should act like refcount_inc() above from saturated. */
void lkdtm_REFCOUNT_DEC_SATURATED(void)
{
refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
pr_info("attempting bad refcount_dec() from saturated\n");
refcount_dec(&sat);
check_saturated(&sat);
}
/* Should act like refcount_inc() above from saturated. */
void lkdtm_REFCOUNT_ADD_SATURATED(void)
{
refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
pr_info("attempting bad refcount_dec() from saturated\n");
refcount_add(8, &sat);
check_saturated(&sat);
}
/* Should act like refcount_inc() above from saturated. */
void lkdtm_REFCOUNT_INC_NOT_ZERO_SATURATED(void)
{
refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
pr_info("attempting bad refcount_inc_not_zero() from saturated\n");
if (!refcount_inc_not_zero(&sat))
pr_warn("Weird: refcount_inc_not_zero() reported zero\n");
check_saturated(&sat);
}
/* Should act like refcount_inc() above from saturated. */
void lkdtm_REFCOUNT_ADD_NOT_ZERO_SATURATED(void)
{
refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
pr_info("attempting bad refcount_add_not_zero() from saturated\n");
if (!refcount_add_not_zero(7, &sat))
pr_warn("Weird: refcount_add_not_zero() reported zero\n");
check_saturated(&sat);
}
/* Should act like refcount_inc() above from saturated. */
void lkdtm_REFCOUNT_DEC_AND_TEST_SATURATED(void)
{
refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
pr_info("attempting bad refcount_dec_and_test() from saturated\n");
if (refcount_dec_and_test(&sat))
pr_warn("Weird: refcount_dec_and_test() reported zero\n");
check_saturated(&sat);
}
/* Should act like refcount_inc() above from saturated. */
void lkdtm_REFCOUNT_SUB_AND_TEST_SATURATED(void)
{
refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
pr_info("attempting bad refcount_sub_and_test() from saturated\n");
if (refcount_sub_and_test(8, &sat))
pr_warn("Weird: refcount_sub_and_test() reported zero\n");
check_saturated(&sat);
}
/* Used to time the existing atomic_t when used for reference counting */
void lkdtm_ATOMIC_TIMING(void)
{
unsigned int i;
atomic_t count = ATOMIC_INIT(1);
for (i = 0; i < INT_MAX - 1; i++)
atomic_inc(&count);
for (i = INT_MAX; i > 0; i--)
if (atomic_dec_and_test(&count))
break;
if (i != 1)
pr_err("atomic timing: out of sync up/down cycle: %u\n", i - 1);
else
pr_info("atomic timing: done\n");
}
/*
* This can be compared to ATOMIC_TIMING when implementing fast refcount
* protections. Looking at the number of CPU cycles tells the real story
* about performance. For example:
* cd /sys/kernel/debug/provoke-crash
* perf stat -B -- cat <(echo REFCOUNT_TIMING) > DIRECT
*/
void lkdtm_REFCOUNT_TIMING(void)
{
unsigned int i;
refcount_t count = REFCOUNT_INIT(1);
for (i = 0; i < INT_MAX - 1; i++)
refcount_inc(&count);
for (i = INT_MAX; i > 0; i--)
if (refcount_dec_and_test(&count))
break;
if (i != 1)
pr_err("refcount: out of sync up/down cycle: %u\n", i - 1);
else
pr_info("refcount timing: done\n");
}