1 files changed, 14 insertions, 43 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0126c9c80c58..8da132a1ef28 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12726,26 +12726,6 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	return 0;
 }
 
-static bool signed_sub_overflows(s64 a, s64 b)
-{
-	/* Do the sub in u64, where overflow is well-defined */
-	s64 res = (s64)((u64)a - (u64)b);
-
-	if (b < 0)
-		return res < a;
-	return res > a;
-}
-
-static bool signed_sub32_overflows(s32 a, s32 b)
-{
-	/* Do the sub in u32, where overflow is well-defined */
-	s32 res = (s32)((u32)a - (u32)b);
-
-	if (b < 0)
-		return res < a;
-	return res > a;
-}
-
 static bool check_reg_sane_offset(struct bpf_verifier_env *env,
 				  const struct bpf_reg_state *reg,
 				  enum bpf_reg_type type)
@@ -13278,14 +13258,11 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		/* A new variable offset is created.  If the subtrahend is known
 		 * nonnegative, then any reg->range we had before is still good.
 		 */
-		if (signed_sub_overflows(smin_ptr, smax_val) ||
-		    signed_sub_overflows(smax_ptr, smin_val)) {
+		if (check_sub_overflow(smin_ptr, smax_val, &dst_reg->smin_value) ||
+		    check_sub_overflow(smax_ptr, smin_val, &dst_reg->smax_value)) {
 			/* Overflow possible, we know nothing */
 			dst_reg->smin_value = S64_MIN;
 			dst_reg->smax_value = S64_MAX;
-		} else {
-			dst_reg->smin_value = smin_ptr - smax_val;
-			dst_reg->smax_value = smax_ptr - smin_val;
 		}
 		if (umin_ptr < umax_val) {
 			/* Overflow possible, we know nothing */
@@ -13378,19 +13355,16 @@ static void scalar_min_max_add(struct bpf_reg_state *dst_reg,
 static void scalar32_min_max_sub(struct bpf_reg_state *dst_reg,
 				 struct bpf_reg_state *src_reg)
 {
-	s32 smin_val = src_reg->s32_min_value;
-	s32 smax_val = src_reg->s32_max_value;
+	s32 *dst_smin = &dst_reg->s32_min_value;
+	s32 *dst_smax = &dst_reg->s32_max_value;
 	u32 umin_val = src_reg->u32_min_value;
 	u32 umax_val = src_reg->u32_max_value;
 
-	if (signed_sub32_overflows(dst_reg->s32_min_value, smax_val) ||
-	    signed_sub32_overflows(dst_reg->s32_max_value, smin_val)) {
+	if (check_sub_overflow(*dst_smin, src_reg->s32_max_value, dst_smin) ||
+	    check_sub_overflow(*dst_smax, src_reg->s32_min_value, dst_smax)) {
 		/* Overflow possible, we know nothing */
-		dst_reg->s32_min_value = S32_MIN;
-		dst_reg->s32_max_value = S32_MAX;
-	} else {
-		dst_reg->s32_min_value -= smax_val;
-		dst_reg->s32_max_value -= smin_val;
+		*dst_smin = S32_MIN;
+		*dst_smax = S32_MAX;
 	}
 	if (dst_reg->u32_min_value < umax_val) {
 		/* Overflow possible, we know nothing */
@@ -13406,19 +13380,16 @@ static void scalar32_min_max_sub(struct bpf_reg_state *dst_reg,
 static void scalar_min_max_sub(struct bpf_reg_state *dst_reg,
 			       struct bpf_reg_state *src_reg)
 {
-	s64 smin_val = src_reg->smin_value;
-	s64 smax_val = src_reg->smax_value;
+	s64 *dst_smin = &dst_reg->smin_value;
+	s64 *dst_smax = &dst_reg->smax_value;
 	u64 umin_val = src_reg->umin_value;
 	u64 umax_val = src_reg->umax_value;
 
-	if (signed_sub_overflows(dst_reg->smin_value, smax_val) ||
-	    signed_sub_overflows(dst_reg->smax_value, smin_val)) {
+	if (check_sub_overflow(*dst_smin, src_reg->smax_value, dst_smin) ||
+	    check_sub_overflow(*dst_smax, src_reg->smin_value, dst_smax)) {
 		/* Overflow possible, we know nothing */
-		dst_reg->smin_value = S64_MIN;
-		dst_reg->smax_value = S64_MAX;
-	} else {
-		dst_reg->smin_value -= smax_val;
-		dst_reg->smax_value -= smin_val;
+		*dst_smin = S64_MIN;
+		*dst_smax = S64_MAX;
 	}
 	if (dst_reg->umin_value < umax_val) {
 		/* Overflow possible, we know nothing */