Merge tag 'hardening-v6.1-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull hardening fixes from Kees Cook:

 - Fix older Clang vs recent overflow KUnit test additions (Nick
   Desaulniers, Kees Cook)

 - Fix kern-doc visibility for overflow helpers (Kees Cook)

* tag 'hardening-v6.1-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  overflow: Refactor test skips for Clang-specific issues
  overflow: disable failing tests for older clang versions
  overflow: Fix kern-doc markup for functions

Documentation/core-api/kernel-api.rst

@@ -118,6 +118,12 @@ Text Searching
 CRC and Math Functions in Linux
 ===============================
 
+Arithmetic Overflow Checking
+----------------------------
+
+.. kernel-doc:: include/linux/overflow.h
+   :internal:
+
 CRC Functions
 -------------
 

Documentation/driver-api/basics.rst

@@ -107,9 +107,6 @@ Kernel utility functions
 .. kernel-doc:: kernel/panic.c
    :export:
 
-.. kernel-doc:: include/linux/overflow.h
-   :internal:
-
 Device Resource Management
 --------------------------
 

include/linux/overflow.h

@@ -51,8 +51,8 @@ static inline bool __must_check __must_check_overflow(bool overflow)
 	return unlikely(overflow);
 }
 
-/** check_add_overflow() - Calculate addition with overflow checking
- *
+/**
+ * check_add_overflow() - Calculate addition with overflow checking
  * @a: first addend
  * @b: second addend
  * @d: pointer to store sum
@@ -66,8 +66,8 @@ static inline bool __must_check __must_check_overflow(bool overflow)
 #define check_add_overflow(a, b, d)	\
 	__must_check_overflow(__builtin_add_overflow(a, b, d))
 
-/** check_sub_overflow() - Calculate subtraction with overflow checking
- *
+/**
+ * check_sub_overflow() - Calculate subtraction with overflow checking
  * @a: minuend; value to subtract from
  * @b: subtrahend; value to subtract from @a
  * @d: pointer to store difference
@@ -81,8 +81,8 @@ static inline bool __must_check __must_check_overflow(bool overflow)
 #define check_sub_overflow(a, b, d)	\
 	__must_check_overflow(__builtin_sub_overflow(a, b, d))
 
-/** check_mul_overflow() - Calculate multiplication with overflow checking
- *
+/**
+ * check_mul_overflow() - Calculate multiplication with overflow checking
  * @a: first factor
  * @b: second factor
  * @d: pointer to store product
@@ -96,23 +96,24 @@ static inline bool __must_check __must_check_overflow(bool overflow)
 #define check_mul_overflow(a, b, d)	\
 	__must_check_overflow(__builtin_mul_overflow(a, b, d))
 
-/** check_shl_overflow() - Calculate a left-shifted value and check overflow
- *
+/**
+ * check_shl_overflow() - Calculate a left-shifted value and check overflow
  * @a: Value to be shifted
  * @s: How many bits left to shift
  * @d: Pointer to where to store the result
  *
  * Computes *@d = (@a << @s)
  *
- * Returns true if '*d' cannot hold the result or when 'a << s' doesn't
+ * Returns true if '*@d' cannot hold the result or when '@a << @s' doesn't
  * make sense. Example conditions:
- * - 'a << s' causes bits to be lost when stored in *d.
- * - 's' is garbage (e.g. negative) or so large that the result of
- *   'a << s' is guaranteed to be 0.
- * - 'a' is negative.
- * - 'a << s' sets the sign bit, if any, in '*d'.
  *
- * '*d' will hold the results of the attempted shift, but is not
+ * - '@a << @s' causes bits to be lost when stored in *@d.
+ * - '@s' is garbage (e.g. negative) or so large that the result of
+ *   '@a << @s' is guaranteed to be 0.
+ * - '@a' is negative.
+ * - '@a << @s' sets the sign bit, if any, in '*@d'.
+ *
+ * '*@d' will hold the results of the attempted shift, but is not
  * considered "safe for use" if true is returned.
  */
 #define check_shl_overflow(a, s, d) __must_check_overflow(({		\
@@ -129,7 +130,6 @@ static inline bool __must_check __must_check_overflow(bool overflow)
 
 /**
  * size_mul() - Calculate size_t multiplication with saturation at SIZE_MAX
- *
  * @factor1: first factor
  * @factor2: second factor
  *
@@ -149,7 +149,6 @@ static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
 
 /**
  * size_add() - Calculate size_t addition with saturation at SIZE_MAX
- *
  * @addend1: first addend
  * @addend2: second addend
  *
@@ -169,7 +168,6 @@ static inline size_t __must_check size_add(size_t addend1, size_t addend2)
 
 /**
  * size_sub() - Calculate size_t subtraction with saturation at SIZE_MAX
- *
  * @minuend: value to subtract from
  * @subtrahend: value to subtract from @minuend
  *
@@ -192,7 +190,6 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
 
 /**
  * array_size() - Calculate size of 2-dimensional array.
- *
  * @a: dimension one
  * @b: dimension two
  *
@@ -205,7 +202,6 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
 
 /**
  * array3_size() - Calculate size of 3-dimensional array.
- *
  * @a: dimension one
  * @b: dimension two
  * @c: dimension three
@@ -220,7 +216,6 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
 /**
  * flex_array_size() - Calculate size of a flexible array member
  *                     within an enclosing structure.
- *
  * @p: Pointer to the structure.
  * @member: Name of the flexible array member.
  * @count: Number of elements in the array.
@@ -237,7 +232,6 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
 
 /**
  * struct_size() - Calculate size of structure with trailing flexible array.
- *
  * @p: Pointer to the structure.
  * @member: Name of the array member.
  * @count: Number of elements in the array.

lib/overflow_kunit.c

@@ -16,6 +16,34 @@
 #include <linux/types.h>
 #include <linux/vmalloc.h>
 
+#define SKIP(cond, reason)		do {			\
+	if (cond) {						\
+		kunit_skip(test, reason);			\
+		return;						\
+	}							\
+} while (0)
+
+/*
+ * Clang 11 and earlier generate unwanted libcalls for signed output
+ * on unsigned input.
+ */
+#if defined(CONFIG_CC_IS_CLANG) && __clang_major__ <= 11
+# define SKIP_SIGN_MISMATCH(t)	SKIP(t, "Clang 11 unwanted libcalls")
+#else
+# define SKIP_SIGN_MISMATCH(t)	do { } while (0)
+#endif
+
+/*
+ * Clang 13 and earlier generate unwanted libcalls for 64-bit tests on
+ * 32-bit hosts.
+ */
+#if defined(CONFIG_CC_IS_CLANG) && __clang_major__ <= 13 &&	\
+    BITS_PER_LONG != 64
+# define SKIP_64_ON_32(t)	SKIP(t, "Clang 13 unwanted libcalls")
+#else
+# define SKIP_64_ON_32(t)	do { } while (0)
+#endif
+
 #define DEFINE_TEST_ARRAY_TYPED(t1, t2, t)			\
 	static const struct test_ ## t1 ## _ ## t2 ## __ ## t {	\
 		t1 a;						\
@@ -94,7 +122,6 @@ DEFINE_TEST_ARRAY(u32) = {
 	{-4U, 5U, 1U, -9U, -20U, true, false, true},
 };
 
-#if BITS_PER_LONG == 64
 DEFINE_TEST_ARRAY(u64) = {
 	{0, 0, 0, 0, 0, false, false, false},
 	{1, 1, 2, 0, 1, false, false, false},
@@ -118,7 +145,6 @@ DEFINE_TEST_ARRAY(u64) = {
 	 false, true, false},
 	{-15ULL, 10ULL, -5ULL, -25ULL, -150ULL, false, false, true},
 };
-#endif
 
 DEFINE_TEST_ARRAY(s8) = {
 	{0, 0, 0, 0, 0, false, false, false},
@@ -194,7 +220,6 @@ DEFINE_TEST_ARRAY(s32) = {
 	{S32_MAX, S32_MAX, -2, 0, 1, true, false, true},
 };
 
-#if BITS_PER_LONG == 64
 DEFINE_TEST_ARRAY(s64) = {
 	{0, 0, 0, 0, 0, false, false, false},
 
@@ -223,7 +248,6 @@ DEFINE_TEST_ARRAY(s64) = {
 	{-128, -1, -129, -127, 128, false, false, false},
 	{0, -S64_MAX, -S64_MAX, S64_MAX, 0, false, false, false},
 };
-#endif
 
 #define check_one_op(t, fmt, op, sym, a, b, r, of) do {			\
 	int _a_orig = a, _a_bump = a + 1;				\
@@ -257,6 +281,12 @@ static void do_test_ ## n(struct kunit *test, const struct test_ ## n *p) \
 static void n ## _overflow_test(struct kunit *test) {			\
 	unsigned i;							\
 									\
+	SKIP_64_ON_32(__same_type(t, u64));				\
+	SKIP_64_ON_32(__same_type(t, s64));				\
+	SKIP_SIGN_MISMATCH(__same_type(n ## _tests[0].a, u32) &&	\
+			   __same_type(n ## _tests[0].b, u32) &&	\
+			   __same_type(n ## _tests[0].sum, int));	\
+									\
 	for (i = 0; i < ARRAY_SIZE(n ## _tests); ++i)			\
 		do_test_ ## n(test, &n ## _tests[i]);			\
 	kunit_info(test, "%zu %s arithmetic tests finished\n",		\
@@ -272,10 +302,8 @@ DEFINE_TEST_FUNC(u16, "%d");
 DEFINE_TEST_FUNC(s16, "%d");
 DEFINE_TEST_FUNC(u32, "%u");
 DEFINE_TEST_FUNC(s32, "%d");
-#if BITS_PER_LONG == 64
 DEFINE_TEST_FUNC(u64, "%llu");
 DEFINE_TEST_FUNC(s64, "%lld");
-#endif
 
 DEFINE_TEST_ARRAY_TYPED(u32, u32, u8) = {
 	{0, 0, 0, 0, 0, false, false, false},
@@ -715,13 +743,10 @@ static struct kunit_case overflow_test_cases[] = {
 	KUNIT_CASE(s16_s16__s16_overflow_test),
 	KUNIT_CASE(u32_u32__u32_overflow_test),
 	KUNIT_CASE(s32_s32__s32_overflow_test),
-/* Clang 13 and earlier generate unwanted libcalls on 32-bit. */
-#if BITS_PER_LONG == 64
 	KUNIT_CASE(u64_u64__u64_overflow_test),
 	KUNIT_CASE(s64_s64__s64_overflow_test),
-#endif
-	KUNIT_CASE(u32_u32__u8_overflow_test),
 	KUNIT_CASE(u32_u32__int_overflow_test),
+	KUNIT_CASE(u32_u32__u8_overflow_test),
 	KUNIT_CASE(u8_u8__int_overflow_test),
 	KUNIT_CASE(int_int__u8_overflow_test),
 	KUNIT_CASE(shift_sane_test),