Merge branch 'bpf-verifier-retval-logic-fixes'

Andrii Nakryiko says:

====================
BPF verifier retval logic fixes

This patch set fixes BPF verifier logic around validating and enforcing return
values for BPF programs that have specific range of expected return values.
Both sync and async callbacks have similar logic and are fixes as well.
A few tests are added that would fail without the fixes in this patch set.

Also, while at it, we update retval checking logic to use smin/smax range
instead of tnum, avoiding future potential issues if expected range cannot be
represented precisely by tnum (e.g., [0, 2] is not representable by tnum and
is treated as [0, 3]).

There is a little bit of refactoring to unify async callback and program exit
logic to avoid duplication of checks as much as possible.

v4->v5:
  - fix timer_bad_ret test on no-alu32 flavor (CI);
v3->v4:
  - add back bpf_func_state rearrangement patch;
  - simplified patch #4 as suggested (Shung-Hsi);
v2->v3:
  - more carefullly switch from umin/umax to smin/smax;
v1->v2:
  - drop tnum from retval checks (Eduard);
  - use smin/smax instead of umin/umax (Alexei).
====================

Link: https://lore.kernel.org/r/20231202175705.885270-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

15 files changed, 212 insertions, 80 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index d99a636d36a7..3378cc753061 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -275,6 +275,11 @@ struct bpf_reference_state {
 	int callback_ref;
 };
 
+struct bpf_retval_range {
+	s32 minval;
+	s32 maxval;
+};
+
 /* state of the program:
  * type of all registers and stack info
  */
@@ -297,8 +302,8 @@ struct bpf_func_state {
 	 * void foo(void) { bpf_timer_set_callback(,foo); }
 	 */
 	u32 async_entry_cnt;
+	struct bpf_retval_range callback_ret_range;
 	bool in_callback_fn;
-	struct tnum callback_ret_range;
 	bool in_async_callback_fn;
 	bool in_exception_callback_fn;
 	/* For callback calling functions that limit number of possible
@@ -316,8 +321,8 @@ struct bpf_func_state {
 	/* The following fields should be last. See copy_func_state() */
 	int acquired_refs;
 	struct bpf_reference_state *refs;
-	int allocated_stack;
 	struct bpf_stack_state *stack;
+	int allocated_stack;
 };
 
 struct bpf_idx_pair {
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 3505f3e5ae96..55d019f30e91 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -539,6 +539,19 @@ static void verbose_snum(struct bpf_verifier_env *env, s64 num)
 		verbose(env, "%#llx", num);
 }
 
+int tnum_strn(char *str, size_t size, struct tnum a)
+{
+	/* print as a constant, if tnum is fully known */
+	if (a.mask == 0) {
+		if (is_unum_decimal(a.value))
+			return snprintf(str, size, "%llu", a.value);
+		else
+			return snprintf(str, size, "%#llx", a.value);
+	}
+	return snprintf(str, size, "(%#llx; %#llx)", a.value, a.mask);
+}
+EXPORT_SYMBOL_GPL(tnum_strn);
+
 static void print_scalar_ranges(struct bpf_verifier_env *env,
 				const struct bpf_reg_state *reg,
 				const char **sep)
diff --git a/kernel/bpf/tnum.c b/kernel/bpf/tnum.c
index f4c91c9b27d7..9dbc31b25e3d 100644
--- a/kernel/bpf/tnum.c
+++ b/kernel/bpf/tnum.c
@@ -172,12 +172,6 @@ bool tnum_in(struct tnum a, struct tnum b)
 	return a.value == b.value;
 }
 
-int tnum_strn(char *str, size_t size, struct tnum a)
-{
-	return snprintf(str, size, "(%#llx; %#llx)", a.value, a.mask);
-}
-EXPORT_SYMBOL_GPL(tnum_strn);
-
 int tnum_sbin(char *str, size_t size, struct tnum a)
 {
 	size_t n;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8e7b6072e3f4..2cd150d6d141 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -362,20 +362,23 @@ __printf(2, 3) static void verbose(void *private_data, const char *fmt, ...)
 
 static void verbose_invalid_scalar(struct bpf_verifier_env *env,
 				   struct bpf_reg_state *reg,
-				   struct tnum *range, const char *ctx,
+				   struct bpf_retval_range range, const char *ctx,
 				   const char *reg_name)
 {
-	char tn_buf[48];
+	bool unknown = true;
 
-	verbose(env, "At %s the register %s ", ctx, reg_name);
-	if (!tnum_is_unknown(reg->var_off)) {
-		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
-		verbose(env, "has value %s", tn_buf);
-	} else {
-		verbose(env, "has unknown scalar value");
+	verbose(env, "%s the register %s has", ctx, reg_name);
+	if (reg->smin_value > S64_MIN) {
+		verbose(env, " smin=%lld", reg->smin_value);
+		unknown = false;
 	}
-	tnum_strn(tn_buf, sizeof(tn_buf), *range);
-	verbose(env, " should have been in %s\n", tn_buf);
+	if (reg->smax_value < S64_MAX) {
+		verbose(env, " smax=%lld", reg->smax_value);
+		unknown = false;
+	}
+	if (unknown)
+		verbose(env, " unknown scalar value");
+	verbose(env, " should have been in [%d, %d]\n", range.minval, range.maxval);
 }
 
 static bool type_may_be_null(u32 type)
@@ -2305,6 +2308,11 @@ static void init_reg_state(struct bpf_verifier_env *env,
 	regs[BPF_REG_FP].frameno = state->frameno;
 }
 
+static struct bpf_retval_range retval_range(s32 minval, s32 maxval)
+{
+	return (struct bpf_retval_range){ minval, maxval };
+}
+
 #define BPF_MAIN_FUNC (-1)
 static void init_func_state(struct bpf_verifier_env *env,
 			    struct bpf_func_state *state,
@@ -2313,7 +2321,7 @@ static void init_func_state(struct bpf_verifier_env *env,
 	state->callsite = callsite;
 	state->frameno = frameno;
 	state->subprogno = subprogno;
-	state->callback_ret_range = tnum_range(0, 0);
+	state->callback_ret_range = retval_range(0, 0);
 	init_reg_state(env, state);
 	mark_verifier_state_scratched(env);
 }
@@ -9396,7 +9404,7 @@ static int set_map_elem_callback_state(struct bpf_verifier_env *env,
 		return err;
 
 	callee->in_callback_fn = true;
-	callee->callback_ret_range = tnum_range(0, 1);
+	callee->callback_ret_range = retval_range(0, 1);
 	return 0;
 }
 
@@ -9418,7 +9426,7 @@ static int set_loop_callback_state(struct bpf_verifier_env *env,
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
 
 	callee->in_callback_fn = true;
-	callee->callback_ret_range = tnum_range(0, 1);
+	callee->callback_ret_range = retval_range(0, 1);
 	return 0;
 }
 
@@ -9448,7 +9456,7 @@ static int set_timer_callback_state(struct bpf_verifier_env *env,
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_4]);
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
 	callee->in_async_callback_fn = true;
-	callee->callback_ret_range = tnum_range(0, 1);
+	callee->callback_ret_range = retval_range(0, 1);
 	return 0;
 }
 
@@ -9476,7 +9484,7 @@ static int set_find_vma_callback_state(struct bpf_verifier_env *env,
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_4]);
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
 	callee->in_callback_fn = true;
-	callee->callback_ret_range = tnum_range(0, 1);
+	callee->callback_ret_range = retval_range(0, 1);
 	return 0;
 }
 
@@ -9499,7 +9507,7 @@ static int set_user_ringbuf_callback_state(struct bpf_verifier_env *env,
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
 
 	callee->in_callback_fn = true;
-	callee->callback_ret_range = tnum_range(0, 1);
+	callee->callback_ret_range = retval_range(0, 1);
 	return 0;
 }
 
@@ -9531,7 +9539,7 @@ static int set_rbtree_add_callback_state(struct bpf_verifier_env *env,
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_4]);
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
 	callee->in_callback_fn = true;
-	callee->callback_ret_range = tnum_range(0, 1);
+	callee->callback_ret_range = retval_range(0, 1);
 	return 0;
 }
 
@@ -9560,6 +9568,11 @@ static bool in_rbtree_lock_required_cb(struct bpf_verifier_env *env)
 	return is_rbtree_lock_required_kfunc(kfunc_btf_id);
 }
 
+static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state *reg)
+{
+	return range.minval <= reg->smin_value && reg->smax_value <= range.maxval;
+}
+
 static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
 {
 	struct bpf_verifier_state *state = env->cur_state, *prev_st;
@@ -9583,15 +9596,21 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
 
 	caller = state->frame[state->curframe - 1];
 	if (callee->in_callback_fn) {
-		/* enforce R0 return value range [0, 1]. */
-		struct tnum range = callee->callback_ret_range;
-
 		if (r0->type != SCALAR_VALUE) {
 			verbose(env, "R0 not a scalar value\n");
 			return -EACCES;
 		}
-		if (!tnum_in(range, r0->var_off)) {
-			verbose_invalid_scalar(env, r0, &range, "callback return", "R0");
+
+		/* we are going to rely on register's precise value */
+		err = mark_reg_read(env, r0, r0->parent, REG_LIVE_READ64);
+		err = err ?: mark_chain_precision(env, BPF_REG_0);
+		if (err)
+			return err;
+
+		/* enforce R0 return value range */
+		if (!retval_range_within(callee->callback_ret_range, r0)) {
+			verbose_invalid_scalar(env, r0, callee->callback_ret_range,
+					       "At callback return", "R0");
 			return -EINVAL;
 		}
 		if (!calls_callback(env, callee->callsite)) {
@@ -11805,7 +11824,7 @@ static int fetch_kfunc_meta(struct bpf_verifier_env *env,
 	return 0;
 }
 
-static int check_return_code(struct bpf_verifier_env *env, int regno);
+static int check_return_code(struct bpf_verifier_env *env, int regno, const char *reg_name);
 
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
@@ -11942,7 +11961,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		 * to bpf_throw becomes the return value of the program.
 		 */
 		if (!env->exception_callback_subprog) {
-			err = check_return_code(env, BPF_REG_1);
+			err = check_return_code(env, BPF_REG_1, "R1");
 			if (err < 0)
 				return err;
 		}
@@ -14972,12 +14991,13 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	return 0;
 }
 
-static int check_return_code(struct bpf_verifier_env *env, int regno)
+static int check_return_code(struct bpf_verifier_env *env, int regno, const char *reg_name)
 {
+	const char *exit_ctx = "At program exit";
 	struct tnum enforce_attach_type_range = tnum_unknown;
 	const struct bpf_prog *prog = env->prog;
 	struct bpf_reg_state *reg;
-	struct tnum range = tnum_range(0, 1), const_0 = tnum_const(0);
+	struct bpf_retval_range range = retval_range(0, 1);
 	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
 	int err;
 	struct bpf_func_state *frame = env->cur_state->frame[0];
@@ -15019,17 +15039,9 @@ static int check_return_code(struct bpf_verifier_env *env, int regno)
 
 	if (frame->in_async_callback_fn) {
 		/* enforce return zero from async callbacks like timer */
-		if (reg->type != SCALAR_VALUE) {
-			verbose(env, "In async callback the register R%d is not a known value (%s)\n",
-				regno, reg_type_str(env, reg->type));
-			return -EINVAL;
-		}
-
-		if (!tnum_in(const_0, reg->var_off)) {
-			verbose_invalid_scalar(env, reg, &const_0, "async callback", "R0");
-			return -EINVAL;
-		}
-		return 0;
+		exit_ctx = "At async callback return";
+		range = retval_range(0, 0);
+		goto enforce_retval;
 	}
 
 	if (is_subprog && !frame->in_exception_callback_fn) {
@@ -15052,14 +15064,14 @@ static int check_return_code(struct bpf_verifier_env *env, int regno)
 		    env->prog->expected_attach_type == BPF_CGROUP_INET4_GETSOCKNAME ||
 		    env->prog->expected_attach_type == BPF_CGROUP_INET6_GETSOCKNAME ||
 		    env->prog->expected_attach_type == BPF_CGROUP_UNIX_GETSOCKNAME)
-			range = tnum_range(1, 1);
+			range = retval_range(1, 1);
 		if (env->prog->expected_attach_type == BPF_CGROUP_INET4_BIND ||
 		    env->prog->expected_attach_type == BPF_CGROUP_INET6_BIND)
-			range = tnum_range(0, 3);
+			range = retval_range(0, 3);
 		break;
 	case BPF_PROG_TYPE_CGROUP_SKB:
 		if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS) {
-			range = tnum_range(0, 3);
+			range = retval_range(0, 3);
 			enforce_attach_type_range = tnum_range(2, 3);
 		}
 		break;
@@ -15072,13 +15084,13 @@ static int check_return_code(struct bpf_verifier_env *env, int regno)
 	case BPF_PROG_TYPE_RAW_TRACEPOINT:
 		if (!env->prog->aux->attach_btf_id)
 			return 0;
-		range = tnum_const(0);
+		range = retval_range(0, 0);
 		break;
 	case BPF_PROG_TYPE_TRACING:
 		switch (env->prog->expected_attach_type) {
 		case BPF_TRACE_FENTRY:
 		case BPF_TRACE_FEXIT:
-			range = tnum_const(0);
+			range = retval_range(0, 0);
 			break;
 		case BPF_TRACE_RAW_TP:
 		case BPF_MODIFY_RETURN:
@@ -15090,7 +15102,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno)
 		}
 		break;
 	case BPF_PROG_TYPE_SK_LOOKUP:
-		range = tnum_range(SK_DROP, SK_PASS);
+		range = retval_range(SK_DROP, SK_PASS);
 		break;
 
 	case BPF_PROG_TYPE_LSM:
@@ -15104,12 +15116,12 @@ static int check_return_code(struct bpf_verifier_env *env, int regno)
 			/* Make sure programs that attach to void
 			 * hooks don't try to modify return value.
 			 */
-			range = tnum_range(1, 1);
+			range = retval_range(1, 1);
 		}
 		break;
 
 	case BPF_PROG_TYPE_NETFILTER:
-		range = tnum_range(NF_DROP, NF_ACCEPT);
+		range = retval_range(NF_DROP, NF_ACCEPT);
 		break;
 	case BPF_PROG_TYPE_EXT:
 		/* freplace program can return anything as its return value
@@ -15119,15 +15131,21 @@ static int check_return_code(struct bpf_verifier_env *env, int regno)
 		return 0;
 	}
 
+enforce_retval:
 	if (reg->type != SCALAR_VALUE) {
-		verbose(env, "At program exit the register R%d is not a known value (%s)\n",
-			regno, reg_type_str(env, reg->type));
+		verbose(env, "%s the register R%d is not a known value (%s)\n",
+			exit_ctx, regno, reg_type_str(env, reg->type));
 		return -EINVAL;
 	}
 
-	if (!tnum_in(range, reg->var_off)) {
-		verbose_invalid_scalar(env, reg, &range, "program exit", "R0");
-		if (prog->expected_attach_type == BPF_LSM_CGROUP &&
+	err = mark_chain_precision(env, regno);
+	if (err)
+		return err;
+
+	if (!retval_range_within(range, reg)) {
+		verbose_invalid_scalar(env, reg, range, exit_ctx, reg_name);
+		if (!is_subprog &&
+		    prog->expected_attach_type == BPF_LSM_CGROUP &&
 		    prog_type == BPF_PROG_TYPE_LSM &&
 		    !prog->aux->attach_func_proto->type)
 			verbose(env, "Note, BPF_LSM_CGROUP that attach to void LSM hooks can't modify return value!\n");
@@ -17410,7 +17428,7 @@ process_bpf_exit_full:
 					continue;
 				}
 
-				err = check_return_code(env, BPF_REG_0);
+				err = check_return_code(env, BPF_REG_0, "R0");
 				if (err)
 					return err;
 process_bpf_exit:
diff --git a/tools/testing/selftests/bpf/progs/exceptions_assert.c b/tools/testing/selftests/bpf/progs/exceptions_assert.c
index 49efaed143fc..0ef81040da59 100644
--- a/tools/testing/selftests/bpf/progs/exceptions_assert.c
+++ b/tools/testing/selftests/bpf/progs/exceptions_assert.c
@@ -125,7 +125,7 @@ int check_assert_generic(struct __sk_buff *ctx)
 }
 
 SEC("?fentry/bpf_check")
-__failure __msg("At program exit the register R0 has value (0x40; 0x0)")
+__failure __msg("At program exit the register R1 has smin=64 smax=64")
 int check_assert_with_return(void *ctx)
 {
 	bpf_assert_with(!ctx, 64);
diff --git a/tools/testing/selftests/bpf/progs/exceptions_fail.c b/tools/testing/selftests/bpf/progs/exceptions_fail.c
index 8c0ef2742208..9cceb6521143 100644
--- a/tools/testing/selftests/bpf/progs/exceptions_fail.c
+++ b/tools/testing/selftests/bpf/progs/exceptions_fail.c
@@ -308,7 +308,7 @@ int reject_set_exception_cb_bad_ret1(void *ctx)
 }
 
 SEC("?fentry/bpf_check")
-__failure __msg("At program exit the register R0 has value (0x40; 0x0) should")
+__failure __msg("At program exit the register R1 has smin=64 smax=64 should")
 int reject_set_exception_cb_bad_ret2(void *ctx)
 {
 	bpf_throw(64);
diff --git a/tools/testing/selftests/bpf/progs/test_global_func15.c b/tools/testing/selftests/bpf/progs/test_global_func15.c
index b512d6a6c75e..b4e089d6981d 100644
--- a/tools/testing/selftests/bpf/progs/test_global_func15.c
+++ b/tools/testing/selftests/bpf/progs/test_global_func15.c
@@ -13,7 +13,7 @@ __noinline int foo(unsigned int *v)
 }
 
 SEC("cgroup_skb/ingress")
-__failure __msg("At program exit the register R0 has value")
+__failure __msg("At program exit the register R0 has ")
 int global_func15(struct __sk_buff *skb)
 {
 	unsigned int v = 1;
@@ -22,3 +22,35 @@ int global_func15(struct __sk_buff *skb)
 
 	return v;
 }
+
+SEC("cgroup_skb/ingress")
+__log_level(2) __flag(BPF_F_TEST_STATE_FREQ)
+__failure
+/* check that fallthrough code path marks r0 as precise */
+__msg("mark_precise: frame0: regs=r0 stack= before 2: (b7) r0 = 1")
+/* check that branch code path marks r0 as precise */
+__msg("mark_precise: frame0: regs=r0 stack= before 0: (85) call bpf_get_prandom_u32#7")
+__msg("At program exit the register R0 has ")
+__naked int global_func15_tricky_pruning(void)
+{
+	asm volatile (
+		"call %[bpf_get_prandom_u32];"
+		"if r0 s> 1000 goto 1f;"
+		"r0 = 1;"
+	"1:"
+		"goto +0;" /* checkpoint */
+		/* cgroup_skb/ingress program is expected to return [0, 1]
+		 * values, so branch above makes sure that in a fallthrough
+		 * case we have a valid 1 stored in R0 register, but in
+		 * a branch case we assign some random value to R0.  So if
+		 * there is something wrong with precision tracking for R0 at
+		 * program exit, we might erronenously prune branch case,
+		 * because R0 in fallthrough case is imprecise (and thus any
+		 * value is valid from POV of verifier is_state_equal() logic)
+		 */
+		"exit;"
+		:
+		: __imm(bpf_get_prandom_u32)
+		: __clobber_common
+	);
+}
diff --git a/tools/testing/selftests/bpf/progs/timer_failure.c b/tools/testing/selftests/bpf/progs/timer_failure.c
index 226d33b5a05c..9fbc69c77bbb 100644
--- a/tools/testing/selftests/bpf/progs/timer_failure.c
+++ b/tools/testing/selftests/bpf/progs/timer_failure.c
@@ -21,17 +21,37 @@ struct {
 	__type(value, struct elem);
 } timer_map SEC(".maps");
 
-static int timer_cb_ret1(void *map, int *key, struct bpf_timer *timer)
+__naked __noinline __used
+static unsigned long timer_cb_ret_bad()
 {
-	if (bpf_get_smp_processor_id() % 2)
-		return 1;
-	else
-		return 0;
+	asm volatile (
+		"call %[bpf_get_prandom_u32];"
+		"if r0 s> 1000 goto 1f;"
+		"r0 = 0;"
+	"1:"
+		"goto +0;" /* checkpoint */
+		/* async callback is expected to return 0, so branch above
+		 * skipping r0 = 0; should lead to a failure, but if exit
+		 * instruction doesn't enforce r0's precision, this callback
+		 * will be successfully verified
+		 */
+		"exit;"
+		:
+		: __imm(bpf_get_prandom_u32)
+		: __clobber_common
+	);
 }
 
 SEC("fentry/bpf_fentry_test1")
-__failure __msg("should have been in (0x0; 0x0)")
-int BPF_PROG2(test_ret_1, int, a)
+__log_level(2)
+__flag(BPF_F_TEST_STATE_FREQ)
+__failure
+/* check that fallthrough code path marks r0 as precise */
+__msg("mark_precise: frame0: regs=r0 stack= before 22: (b7) r0 = 0")
+/* check that branch code path marks r0 as precise */
+__msg("mark_precise: frame0: regs=r0 stack= before 24: (85) call bpf_get_prandom_u32#7")
+__msg("should have been in [0, 0]")
+long BPF_PROG2(test_bad_ret, int, a)
 {
 	int key = 0;
 	struct bpf_timer *timer;
@@ -39,7 +59,7 @@ int BPF_PROG2(test_ret_1, int, a)
 	timer = bpf_map_lookup_elem(&timer_map, &key);
 	if (timer) {
 		bpf_timer_init(timer, &timer_map, CLOCK_BOOTTIME);
-		bpf_timer_set_callback(timer, timer_cb_ret1);
+		bpf_timer_set_callback(timer, timer_cb_ret_bad);
 		bpf_timer_start(timer, 1000, 0);
 	}
 
diff --git a/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c b/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c
index 03ee946c6bf7..11ab25c42c36 100644
--- a/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c
+++ b/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c
@@ -184,7 +184,7 @@ invalid_drain_callback_return(struct bpf_dynptr *dynptr, void *context)
  * not be able to write to that pointer.
  */
 SEC("?raw_tp")
-__failure __msg("At callback return the register R0 has value")
+__failure __msg("At callback return the register R0 has ")
 int user_ringbuf_callback_invalid_return(void *ctx)
 {
 	bpf_user_ringbuf_drain(&user_ringbuf, invalid_drain_callback_return, NULL, 0);
diff --git a/tools/testing/selftests/bpf/progs/verifier_cgroup_inv_retcode.c b/tools/testing/selftests/bpf/progs/verifier_cgroup_inv_retcode.c
index d6c4a7f3f790..6e0f349f8f15 100644
--- a/tools/testing/selftests/bpf/progs/verifier_cgroup_inv_retcode.c
+++ b/tools/testing/selftests/bpf/progs/verifier_cgroup_inv_retcode.c
@@ -7,7 +7,7 @@
 
 SEC("cgroup/sock")
 __description("bpf_exit with invalid return code. test1")
-__failure __msg("R0 has value (0x0; 0xffffffff)")
+__failure __msg("smin=0 smax=4294967295 should have been in [0, 1]")
 __naked void with_invalid_return_code_test1(void)
 {
 	asm volatile ("					\
@@ -30,7 +30,7 @@ __naked void with_invalid_return_code_test2(void)
 
 SEC("cgroup/sock")
 __description("bpf_exit with invalid return code. test3")
-__failure __msg("R0 has value (0x0; 0x3)")
+__failure __msg("smin=0 smax=3 should have been in [0, 1]")
 __naked void with_invalid_return_code_test3(void)
 {
 	asm volatile ("					\
@@ -53,7 +53,7 @@ __naked void with_invalid_return_code_test4(void)
 
 SEC("cgroup/sock")
 __description("bpf_exit with invalid return code. test5")
-__failure __msg("R0 has value (0x2; 0x0)")
+__failure __msg("smin=2 smax=2 should have been in [0, 1]")
 __naked void with_invalid_return_code_test5(void)
 {
 	asm volatile ("					\
@@ -75,7 +75,7 @@ __naked void with_invalid_return_code_test6(void)
 
 SEC("cgroup/sock")
 __description("bpf_exit with invalid return code. test7")
-__failure __msg("R0 has unknown scalar value")
+__failure __msg("R0 has unknown scalar value should have been in [0, 1]")
 __naked void with_invalid_return_code_test7(void)
 {
 	asm volatile ("					\
diff --git a/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c b/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c
index 99a23dea8233..be95570ab382 100644
--- a/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c
+++ b/tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c
@@ -411,7 +411,7 @@ l0_%=:	r0 = 0;						\
 
 SEC("tc")
 __description("direct packet access: test17 (pruning, alignment)")
-__failure __msg("misaligned packet access off 2+(0x0; 0x0)+15+-4 size 4")
+__failure __msg("misaligned packet access off 2+0+15+-4 size 4")
 __flag(BPF_F_STRICT_ALIGNMENT)
 __naked void packet_access_test17_pruning_alignment(void)
 {
diff --git a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
index b054f9c48143..74d9cad469d9 100644
--- a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
+++ b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
@@ -67,7 +67,7 @@ __naked void ptr_to_long_half_uninitialized(void)
 
 SEC("cgroup/sysctl")
 __description("ARG_PTR_TO_LONG misaligned")
-__failure __msg("misaligned stack access off (0x0; 0x0)+-20+0 size 8")
+__failure __msg("misaligned stack access off 0+-20+0 size 8")
 __naked void arg_ptr_to_long_misaligned(void)
 {
 	asm volatile ("					\
diff --git a/tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c b/tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c
index 353ae6da00e1..e1ffa5d32ff0 100644
--- a/tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c
+++ b/tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c
@@ -39,7 +39,7 @@ __naked void with_valid_return_code_test3(void)
 
 SEC("netfilter")
 __description("bpf_exit with invalid return code. test4")
-__failure __msg("R0 has value (0x2; 0x0)")
+__failure __msg("R0 has smin=2 smax=2 should have been in [0, 1]")
 __naked void with_invalid_return_code_test4(void)
 {
 	asm volatile ("					\
diff --git a/tools/testing/selftests/bpf/progs/verifier_stack_ptr.c b/tools/testing/selftests/bpf/progs/verifier_stack_ptr.c
index e0f77e3e7869..417c61cd4b19 100644
--- a/tools/testing/selftests/bpf/progs/verifier_stack_ptr.c
+++ b/tools/testing/selftests/bpf/progs/verifier_stack_ptr.c
@@ -37,7 +37,7 @@ __naked void ptr_to_stack_store_load(void)
 
 SEC("socket")
 __description("PTR_TO_STACK store/load - bad alignment on off")
-__failure __msg("misaligned stack access off (0x0; 0x0)+-8+2 size 8")
+__failure __msg("misaligned stack access off 0+-8+2 size 8")
 __failure_unpriv
 __naked void load_bad_alignment_on_off(void)
 {
@@ -53,7 +53,7 @@ __naked void load_bad_alignment_on_off(void)
 
 SEC("socket")
 __description("PTR_TO_STACK store/load - bad alignment on reg")
-__failure __msg("misaligned stack access off (0x0; 0x0)+-10+8 size 8")
+__failure __msg("misaligned stack access off 0+-10+8 size 8")
 __failure_unpriv
 __naked void load_bad_alignment_on_reg(void)
 {
diff --git a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
index b5efcaeaa1ae..0dfe3f8b69ac 100644
--- a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
+++ b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c
@@ -117,6 +117,56 @@ __naked int global_subprog_result_precise(void)
 	);
 }
 
+__naked __noinline __used
+static unsigned long loop_callback_bad()
+{
+	/* bpf_loop() callback that can return values outside of [0, 1] range */
+	asm volatile (
+		"call %[bpf_get_prandom_u32];"
+		"if r0 s> 1000 goto 1f;"
+		"r0 = 0;"
+	"1:"
+		"goto +0;" /* checkpoint */
+		/* bpf_loop() expects [0, 1] values, so branch above skipping
+		 * r0 = 0; should lead to a failure, but if exit instruction
+		 * doesn't enforce r0's precision, this callback will be
+		 * successfully verified
+		 */
+		"exit;"
+		:
+		: __imm(bpf_get_prandom_u32)
+		: __clobber_common
+	);
+}
+
+SEC("?raw_tp")
+__failure __log_level(2)
+__flag(BPF_F_TEST_STATE_FREQ)
+/* check that fallthrough code path marks r0 as precise */
+__msg("mark_precise: frame1: regs=r0 stack= before 11: (b7) r0 = 0")
+/* check that we have branch code path doing its own validation */
+__msg("from 10 to 12: frame1: R0=scalar(smin=umin=1001")
+/* check that branch code path marks r0 as precise, before failing */
+__msg("mark_precise: frame1: regs=r0 stack= before 9: (85) call bpf_get_prandom_u32#7")
+__msg("At callback return the register R0 has smin=1001 should have been in [0, 1]")
+__naked int callback_precise_return_fail(void)
+{
+	asm volatile (
+		"r1 = 1;"			/* nr_loops */
+		"r2 = %[loop_callback_bad];"	/* callback_fn */
+		"r3 = 0;"			/* callback_ctx */
+		"r4 = 0;"			/* flags */
+		"call %[bpf_loop];"
+
+		"r0 = 0;"
+		"exit;"
+		:
+		: __imm_ptr(loop_callback_bad),
+		  __imm(bpf_loop)
+		: __clobber_common
+	);
+}
+
 SEC("?raw_tp")
 __success __log_level(2)
 /* First simulated path does not include callback body,