From 44d56761bed0a394cceb4b0c57fee4fc0e4d9a85 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgzones@googlemail.com>
Date: Tue, 6 Jul 2021 19:36:29 +0200
Subject: [PATCH] libsepol: avoid unsigned integer overflow
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Unsigned integer overflow is well-defined and not undefined behavior.
It is commonly used for hashing or pseudo random number generation.
But it is still useful to enable undefined behavior sanitizer checks on
unsigned arithmetic to detect possible issues on counters or variables
with similar purpose or missed overflow checks on user input.

Use a spaceship operator like comparison instead of subtraction.

    policydb.c:851:24: runtime error: unsigned integer overflow: 801 - 929 cannot be represented in type 'unsigned int'

Follow-up of: 1537ea8412e4 ("libsepol: avoid unsigned integer overflow")

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
---
 libsepol/src/policydb.c | 10 +++++-----
 libsepol/src/private.h  |  2 ++
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c
index ef2217c28c91..0398ceed2574 100644
--- a/libsepol/src/policydb.c
+++ b/libsepol/src/policydb.c
@@ -817,11 +817,11 @@ static int filenametr_cmp(hashtab_t h __attribute__ ((unused)),
 	const filename_trans_key_t *ft2 = (const filename_trans_key_t *)k2;
 	int v;
 
-	v = (ft1->ttype > ft2->ttype) - (ft1->ttype < ft2->ttype);
+	v = spaceship_cmp(ft1->ttype, ft2->ttype);
 	if (v)
 		return v;
 
-	v = (ft1->tclass > ft2->tclass) - (ft1->tclass < ft2->tclass);
+	v = spaceship_cmp(ft1->tclass, ft2->tclass);
 	if (v)
 		return v;
 
@@ -843,15 +843,15 @@ static int rangetr_cmp(hashtab_t h __attribute__ ((unused)),
 	const struct range_trans *key2 = (const struct range_trans *)k2;
 	int v;
 
-	v = key1->source_type - key2->source_type;
+	v = spaceship_cmp(key1->source_type, key2->source_type);
 	if (v)
 		return v;
 
-	v = key1->target_type - key2->target_type;
+	v = spaceship_cmp(key1->target_type, key2->target_type);
 	if (v)
 		return v;
 
-	v = key1->target_class - key2->target_class;
+	v = spaceship_cmp(key1->target_class, key2->target_class);
 
 	return v;
 }
diff --git a/libsepol/src/private.h b/libsepol/src/private.h
index 72f212628314..c63238abe5f3 100644
--- a/libsepol/src/private.h
+++ b/libsepol/src/private.h
@@ -47,6 +47,8 @@
 #define is_saturated(x) (x == (typeof(x))-1)
 #define zero_or_saturated(x) ((x == 0) || is_saturated(x))
 
+#define spaceship_cmp(a, b) (((a) > (b)) - ((a) < (b)))
+
 /* Policy compatibility information. */
 struct policydb_compat_info {
 	unsigned int type;
-- 
2.32.0