v4.19.13 snapshot.
diff --git a/drivers/misc/lkdtm/refcount.c b/drivers/misc/lkdtm/refcount.c
new file mode 100644
index 0000000..0a146b3
--- /dev/null
+++ b/drivers/misc/lkdtm/refcount.c
@@ -0,0 +1,401 @@
+// 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");
+}