420 lines
11 KiB
C
420 lines
11 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* This is for all the tests related to refcount bugs (e.g. overflow,
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* underflow, reaching zero untested, etc).
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*/
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#include "lkdtm.h"
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#include <linux/refcount.h>
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static void overflow_check(refcount_t *ref)
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{
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switch (refcount_read(ref)) {
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case REFCOUNT_SATURATED:
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pr_info("Overflow detected: saturated\n");
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break;
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case REFCOUNT_MAX:
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pr_warn("Overflow detected: unsafely reset to max\n");
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break;
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default:
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pr_err("Fail: refcount wrapped to %d\n", refcount_read(ref));
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}
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}
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/*
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* A refcount_inc() above the maximum value of the refcount implementation,
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* should at least saturate, and at most also WARN.
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*/
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static void lkdtm_REFCOUNT_INC_OVERFLOW(void)
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{
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refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX - 1);
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pr_info("attempting good refcount_inc() without overflow\n");
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refcount_dec(&over);
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refcount_inc(&over);
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pr_info("attempting bad refcount_inc() overflow\n");
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refcount_inc(&over);
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refcount_inc(&over);
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overflow_check(&over);
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}
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/* refcount_add() should behave just like refcount_inc() above. */
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static void lkdtm_REFCOUNT_ADD_OVERFLOW(void)
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{
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refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX - 1);
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pr_info("attempting good refcount_add() without overflow\n");
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refcount_dec(&over);
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refcount_dec(&over);
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refcount_dec(&over);
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refcount_dec(&over);
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refcount_add(4, &over);
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pr_info("attempting bad refcount_add() overflow\n");
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refcount_add(4, &over);
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overflow_check(&over);
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}
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/* refcount_inc_not_zero() should behave just like refcount_inc() above. */
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static void lkdtm_REFCOUNT_INC_NOT_ZERO_OVERFLOW(void)
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{
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refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX);
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pr_info("attempting bad refcount_inc_not_zero() overflow\n");
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if (!refcount_inc_not_zero(&over))
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pr_warn("Weird: refcount_inc_not_zero() reported zero\n");
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overflow_check(&over);
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}
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/* refcount_add_not_zero() should behave just like refcount_inc() above. */
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static void lkdtm_REFCOUNT_ADD_NOT_ZERO_OVERFLOW(void)
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{
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refcount_t over = REFCOUNT_INIT(REFCOUNT_MAX);
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pr_info("attempting bad refcount_add_not_zero() overflow\n");
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if (!refcount_add_not_zero(6, &over))
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pr_warn("Weird: refcount_add_not_zero() reported zero\n");
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overflow_check(&over);
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}
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static void check_zero(refcount_t *ref)
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{
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switch (refcount_read(ref)) {
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case REFCOUNT_SATURATED:
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pr_info("Zero detected: saturated\n");
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break;
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case REFCOUNT_MAX:
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pr_warn("Zero detected: unsafely reset to max\n");
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break;
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case 0:
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pr_warn("Still at zero: refcount_inc/add() must not inc-from-0\n");
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break;
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default:
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pr_err("Fail: refcount went crazy: %d\n", refcount_read(ref));
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}
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}
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/*
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* A refcount_dec(), as opposed to a refcount_dec_and_test(), when it hits
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* zero it should either saturate (when inc-from-zero isn't protected)
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* or stay at zero (when inc-from-zero is protected) and should WARN for both.
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*/
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static void lkdtm_REFCOUNT_DEC_ZERO(void)
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{
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refcount_t zero = REFCOUNT_INIT(2);
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pr_info("attempting good refcount_dec()\n");
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refcount_dec(&zero);
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pr_info("attempting bad refcount_dec() to zero\n");
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refcount_dec(&zero);
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check_zero(&zero);
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}
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static void check_negative(refcount_t *ref, int start)
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{
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/*
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* refcount_t refuses to move a refcount at all on an
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* over-sub, so we have to track our starting position instead of
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* looking only at zero-pinning.
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*/
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if (refcount_read(ref) == start) {
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pr_warn("Still at %d: refcount_inc/add() must not inc-from-0\n",
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start);
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return;
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}
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switch (refcount_read(ref)) {
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case REFCOUNT_SATURATED:
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pr_info("Negative detected: saturated\n");
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break;
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case REFCOUNT_MAX:
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pr_warn("Negative detected: unsafely reset to max\n");
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break;
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default:
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pr_err("Fail: refcount went crazy: %d\n", refcount_read(ref));
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}
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}
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/* A refcount_dec() going negative should saturate and may WARN. */
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static void lkdtm_REFCOUNT_DEC_NEGATIVE(void)
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{
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refcount_t neg = REFCOUNT_INIT(0);
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pr_info("attempting bad refcount_dec() below zero\n");
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refcount_dec(&neg);
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check_negative(&neg, 0);
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}
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/*
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* A refcount_dec_and_test() should act like refcount_dec() above when
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* going negative.
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*/
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static void lkdtm_REFCOUNT_DEC_AND_TEST_NEGATIVE(void)
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{
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refcount_t neg = REFCOUNT_INIT(0);
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pr_info("attempting bad refcount_dec_and_test() below zero\n");
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if (refcount_dec_and_test(&neg))
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pr_warn("Weird: refcount_dec_and_test() reported zero\n");
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check_negative(&neg, 0);
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}
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/*
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* A refcount_sub_and_test() should act like refcount_dec_and_test()
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* above when going negative.
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*/
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static void lkdtm_REFCOUNT_SUB_AND_TEST_NEGATIVE(void)
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{
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refcount_t neg = REFCOUNT_INIT(3);
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pr_info("attempting bad refcount_sub_and_test() below zero\n");
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if (refcount_sub_and_test(5, &neg))
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pr_warn("Weird: refcount_sub_and_test() reported zero\n");
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check_negative(&neg, 3);
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}
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static void check_from_zero(refcount_t *ref)
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{
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switch (refcount_read(ref)) {
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case 0:
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pr_info("Zero detected: stayed at zero\n");
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break;
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case REFCOUNT_SATURATED:
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pr_info("Zero detected: saturated\n");
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break;
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case REFCOUNT_MAX:
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pr_warn("Zero detected: unsafely reset to max\n");
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break;
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default:
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pr_info("Fail: zero not detected, incremented to %d\n",
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refcount_read(ref));
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}
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}
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/*
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* A refcount_inc() from zero should pin to zero or saturate and may WARN.
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*/
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static void lkdtm_REFCOUNT_INC_ZERO(void)
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{
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refcount_t zero = REFCOUNT_INIT(0);
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pr_info("attempting safe refcount_inc_not_zero() from zero\n");
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if (!refcount_inc_not_zero(&zero)) {
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pr_info("Good: zero detected\n");
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if (refcount_read(&zero) == 0)
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pr_info("Correctly stayed at zero\n");
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else
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pr_err("Fail: refcount went past zero!\n");
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} else {
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pr_err("Fail: Zero not detected!?\n");
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}
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pr_info("attempting bad refcount_inc() from zero\n");
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refcount_inc(&zero);
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check_from_zero(&zero);
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}
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/*
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* A refcount_add() should act like refcount_inc() above when starting
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* at zero.
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*/
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static void lkdtm_REFCOUNT_ADD_ZERO(void)
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{
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refcount_t zero = REFCOUNT_INIT(0);
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pr_info("attempting safe refcount_add_not_zero() from zero\n");
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if (!refcount_add_not_zero(3, &zero)) {
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pr_info("Good: zero detected\n");
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if (refcount_read(&zero) == 0)
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pr_info("Correctly stayed at zero\n");
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else
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pr_err("Fail: refcount went past zero\n");
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} else {
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pr_err("Fail: Zero not detected!?\n");
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}
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pr_info("attempting bad refcount_add() from zero\n");
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refcount_add(3, &zero);
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check_from_zero(&zero);
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}
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static void check_saturated(refcount_t *ref)
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{
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switch (refcount_read(ref)) {
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case REFCOUNT_SATURATED:
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pr_info("Saturation detected: still saturated\n");
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break;
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case REFCOUNT_MAX:
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pr_warn("Saturation detected: unsafely reset to max\n");
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break;
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default:
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pr_err("Fail: refcount went crazy: %d\n", refcount_read(ref));
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}
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}
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/*
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* A refcount_inc() from a saturated value should at most warn about
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* being saturated already.
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*/
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static void lkdtm_REFCOUNT_INC_SATURATED(void)
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{
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refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
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pr_info("attempting bad refcount_inc() from saturated\n");
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refcount_inc(&sat);
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check_saturated(&sat);
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}
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/* Should act like refcount_inc() above from saturated. */
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static void lkdtm_REFCOUNT_DEC_SATURATED(void)
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{
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refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
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pr_info("attempting bad refcount_dec() from saturated\n");
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refcount_dec(&sat);
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check_saturated(&sat);
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}
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/* Should act like refcount_inc() above from saturated. */
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static void lkdtm_REFCOUNT_ADD_SATURATED(void)
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{
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refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
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pr_info("attempting bad refcount_dec() from saturated\n");
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refcount_add(8, &sat);
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check_saturated(&sat);
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}
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/* Should act like refcount_inc() above from saturated. */
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static void lkdtm_REFCOUNT_INC_NOT_ZERO_SATURATED(void)
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{
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refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
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pr_info("attempting bad refcount_inc_not_zero() from saturated\n");
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if (!refcount_inc_not_zero(&sat))
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pr_warn("Weird: refcount_inc_not_zero() reported zero\n");
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check_saturated(&sat);
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}
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/* Should act like refcount_inc() above from saturated. */
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static void lkdtm_REFCOUNT_ADD_NOT_ZERO_SATURATED(void)
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{
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refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
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pr_info("attempting bad refcount_add_not_zero() from saturated\n");
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if (!refcount_add_not_zero(7, &sat))
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pr_warn("Weird: refcount_add_not_zero() reported zero\n");
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check_saturated(&sat);
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}
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/* Should act like refcount_inc() above from saturated. */
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static void lkdtm_REFCOUNT_DEC_AND_TEST_SATURATED(void)
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{
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refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
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pr_info("attempting bad refcount_dec_and_test() from saturated\n");
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if (refcount_dec_and_test(&sat))
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pr_warn("Weird: refcount_dec_and_test() reported zero\n");
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check_saturated(&sat);
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}
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/* Should act like refcount_inc() above from saturated. */
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static void lkdtm_REFCOUNT_SUB_AND_TEST_SATURATED(void)
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{
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refcount_t sat = REFCOUNT_INIT(REFCOUNT_SATURATED);
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pr_info("attempting bad refcount_sub_and_test() from saturated\n");
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if (refcount_sub_and_test(8, &sat))
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pr_warn("Weird: refcount_sub_and_test() reported zero\n");
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check_saturated(&sat);
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}
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/* Used to time the existing atomic_t when used for reference counting */
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static void lkdtm_ATOMIC_TIMING(void)
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{
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unsigned int i;
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atomic_t count = ATOMIC_INIT(1);
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for (i = 0; i < INT_MAX - 1; i++)
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atomic_inc(&count);
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for (i = INT_MAX; i > 0; i--)
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if (atomic_dec_and_test(&count))
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break;
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if (i != 1)
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pr_err("atomic timing: out of sync up/down cycle: %u\n", i - 1);
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else
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pr_info("atomic timing: done\n");
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}
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/*
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* This can be compared to ATOMIC_TIMING when implementing fast refcount
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* protections. Looking at the number of CPU cycles tells the real story
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* about performance. For example:
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|
* cd /sys/kernel/debug/provoke-crash
|
||
|
|
* perf stat -B -- cat <(echo REFCOUNT_TIMING) > DIRECT
|
||
|
|
*/
|
||
|
|
static 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");
|
||
|
|
}
|
||
|
|
|
||
|
|
static struct crashtype crashtypes[] = {
|
||
|
|
CRASHTYPE(REFCOUNT_INC_OVERFLOW),
|
||
|
|
CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
|
||
|
|
CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
|
||
|
|
CRASHTYPE(REFCOUNT_ADD_NOT_ZERO_OVERFLOW),
|
||
|
|
CRASHTYPE(REFCOUNT_DEC_ZERO),
|
||
|
|
CRASHTYPE(REFCOUNT_DEC_NEGATIVE),
|
||
|
|
CRASHTYPE(REFCOUNT_DEC_AND_TEST_NEGATIVE),
|
||
|
|
CRASHTYPE(REFCOUNT_SUB_AND_TEST_NEGATIVE),
|
||
|
|
CRASHTYPE(REFCOUNT_INC_ZERO),
|
||
|
|
CRASHTYPE(REFCOUNT_ADD_ZERO),
|
||
|
|
CRASHTYPE(REFCOUNT_INC_SATURATED),
|
||
|
|
CRASHTYPE(REFCOUNT_DEC_SATURATED),
|
||
|
|
CRASHTYPE(REFCOUNT_ADD_SATURATED),
|
||
|
|
CRASHTYPE(REFCOUNT_INC_NOT_ZERO_SATURATED),
|
||
|
|
CRASHTYPE(REFCOUNT_ADD_NOT_ZERO_SATURATED),
|
||
|
|
CRASHTYPE(REFCOUNT_DEC_AND_TEST_SATURATED),
|
||
|
|
CRASHTYPE(REFCOUNT_SUB_AND_TEST_SATURATED),
|
||
|
|
CRASHTYPE(ATOMIC_TIMING),
|
||
|
|
CRASHTYPE(REFCOUNT_TIMING),
|
||
|
|
};
|
||
|
|
|
||
|
|
struct crashtype_category refcount_crashtypes = {
|
||
|
|
.crashtypes = crashtypes,
|
||
|
|
.len = ARRAY_SIZE(crashtypes),
|
||
|
|
};
|