diff options
Diffstat (limited to 'drivers/misc/lkdtm/refcount.c')
| -rw-r--r-- | drivers/misc/lkdtm/refcount.c | 419 |
1 files changed, 419 insertions, 0 deletions
diff --git a/drivers/misc/lkdtm/refcount.c b/drivers/misc/lkdtm/refcount.c new file mode 100644 index 0000000000..5cd488f54c --- /dev/null +++ b/drivers/misc/lkdtm/refcount.c @@ -0,0 +1,419 @@ +// 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> + +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. + */ +static 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. */ +static 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. */ +static 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. */ +static 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. + */ +static 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) +{ + /* + * refcount_t 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. */ +static 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. + */ +static 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. + */ +static 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. + */ +static 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. + */ +static 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. + */ +static 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. */ +static 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. */ +static 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. */ +static 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. */ +static 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. */ +static 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. */ +static 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 */ +static 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 + */ +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), +}; |