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Merge tag 'hardening-v6.14-rc1-fix1' of git://git.kernel.org/pub/scm/…
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…linux/kernel/git/kees/linux

Pull hardening fixes from Kees Cook:
 "This is a fix for the soon to be released GCC 15 which has regressed
  its initialization of unions when performing explicit initialization
  (i.e. a general problem, not specifically a hardening problem; we're
  just carrying the fix).

  Details in the final patch, Acked by Masahiro, with updated selftests
  to validate the fix"

* tag 'hardening-v6.14-rc1-fix1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  kbuild: Use -fzero-init-padding-bits=all
  stackinit: Add union initialization to selftests
  stackinit: Add old-style zero-init syntax to struct tests
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Linus Torvalds committed Feb 1, 2025
2 parents 851faa8 + dce4aab commit 73512f2
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106 changes: 106 additions & 0 deletions lib/stackinit_kunit.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,21 +47,26 @@ static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,
#define DO_NOTHING_TYPE_SCALAR(var_type) var_type
#define DO_NOTHING_TYPE_STRING(var_type) void
#define DO_NOTHING_TYPE_STRUCT(var_type) void
#define DO_NOTHING_TYPE_UNION(var_type) void

#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
#define DO_NOTHING_RETURN_STRING(ptr) /**/
#define DO_NOTHING_RETURN_STRUCT(ptr) /**/
#define DO_NOTHING_RETURN_UNION(ptr) /**/

#define DO_NOTHING_CALL_SCALAR(var, name) \
(var) = do_nothing_ ## name(&(var))
#define DO_NOTHING_CALL_STRING(var, name) \
do_nothing_ ## name(var)
#define DO_NOTHING_CALL_STRUCT(var, name) \
do_nothing_ ## name(&(var))
#define DO_NOTHING_CALL_UNION(var, name) \
do_nothing_ ## name(&(var))

#define FETCH_ARG_SCALAR(var) &var
#define FETCH_ARG_STRING(var) var
#define FETCH_ARG_STRUCT(var) &var
#define FETCH_ARG_UNION(var) &var

/*
* On m68k, if the leaf function test variable is longer than 8 bytes,
Expand All @@ -77,6 +82,7 @@ static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,
#define INIT_CLONE_SCALAR /**/
#define INIT_CLONE_STRING [FILL_SIZE_STRING]
#define INIT_CLONE_STRUCT /**/
#define INIT_CLONE_UNION /**/

#define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero))
#define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero))
Expand All @@ -92,6 +98,7 @@ static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,
zero.three = 0; \
zero.four = 0; \
} while (0)
#define ZERO_CLONE_UNION(zero) ZERO_CLONE_STRUCT(zero)

#define INIT_SCALAR_none(var_type) /**/
#define INIT_SCALAR_zero(var_type) = 0
Expand All @@ -101,6 +108,7 @@ static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,

#define INIT_STRUCT_none(var_type) /**/
#define INIT_STRUCT_zero(var_type) = { }
#define INIT_STRUCT_old_zero(var_type) = { 0 }


#define __static_partial { .two = 0, }
Expand Down Expand Up @@ -146,6 +154,34 @@ static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,
#define INIT_STRUCT_assigned_copy(var_type) \
; var = *(arg)

/* Union initialization is the same as structs. */
#define INIT_UNION_none(var_type) INIT_STRUCT_none(var_type)
#define INIT_UNION_zero(var_type) INIT_STRUCT_zero(var_type)
#define INIT_UNION_old_zero(var_type) INIT_STRUCT_old_zero(var_type)

#define INIT_UNION_static_partial(var_type) \
INIT_STRUCT_static_partial(var_type)
#define INIT_UNION_static_all(var_type) \
INIT_STRUCT_static_all(var_type)
#define INIT_UNION_dynamic_partial(var_type) \
INIT_STRUCT_dynamic_partial(var_type)
#define INIT_UNION_dynamic_all(var_type) \
INIT_STRUCT_dynamic_all(var_type)
#define INIT_UNION_runtime_partial(var_type) \
INIT_STRUCT_runtime_partial(var_type)
#define INIT_UNION_runtime_all(var_type) \
INIT_STRUCT_runtime_all(var_type)
#define INIT_UNION_assigned_static_partial(var_type) \
INIT_STRUCT_assigned_static_partial(var_type)
#define INIT_UNION_assigned_static_all(var_type) \
INIT_STRUCT_assigned_static_all(var_type)
#define INIT_UNION_assigned_dynamic_partial(var_type) \
INIT_STRUCT_assigned_dynamic_partial(var_type)
#define INIT_UNION_assigned_dynamic_all(var_type) \
INIT_STRUCT_assigned_dynamic_all(var_type)
#define INIT_UNION_assigned_copy(var_type) \
INIT_STRUCT_assigned_copy(var_type)

/*
* @name: unique string name for the test
* @var_type: type to be tested for zeroing initialization
Expand Down Expand Up @@ -294,6 +330,33 @@ struct test_user {
unsigned long four;
};

/* No padding: all members are the same size. */
union test_same_sizes {
unsigned long one;
unsigned long two;
unsigned long three;
unsigned long four;
};

/* Mismatched sizes, with one and two being small */
union test_small_start {
char one:1;
char two;
short three;
unsigned long four;
struct big_struct {
unsigned long array[8];
} big;
};

/* Mismatched sizes, with one and two being small */
union test_small_end {
short one;
unsigned long two;
char three:1;
char four;
};

#define ALWAYS_PASS WANT_SUCCESS
#define ALWAYS_FAIL XFAIL

Expand Down Expand Up @@ -332,6 +395,11 @@ struct test_user {
struct test_ ## name, STRUCT, init, \
xfail)

#define DEFINE_UNION_TEST(name, init, xfail) \
DEFINE_TEST(name ## _ ## init, \
union test_ ## name, STRUCT, init, \
xfail)

#define DEFINE_STRUCT_TESTS(init, xfail) \
DEFINE_STRUCT_TEST(small_hole, init, xfail); \
DEFINE_STRUCT_TEST(big_hole, init, xfail); \
Expand All @@ -343,16 +411,35 @@ struct test_user {
xfail); \
DEFINE_STRUCT_TESTS(base ## _ ## all, xfail)

#define DEFINE_UNION_INITIALIZER_TESTS(base, xfail) \
DEFINE_UNION_TESTS(base ## _ ## partial, \
xfail); \
DEFINE_UNION_TESTS(base ## _ ## all, xfail)

#define DEFINE_UNION_TESTS(init, xfail) \
DEFINE_UNION_TEST(same_sizes, init, xfail); \
DEFINE_UNION_TEST(small_start, init, xfail); \
DEFINE_UNION_TEST(small_end, init, xfail);

/* These should be fully initialized all the time! */
DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS);
DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS);
DEFINE_STRUCT_TESTS(old_zero, ALWAYS_PASS);
DEFINE_UNION_TESTS(zero, ALWAYS_PASS);
DEFINE_UNION_TESTS(old_zero, ALWAYS_PASS);
/* Struct initializers: padding may be left uninitialized. */
DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL);
DEFINE_UNION_INITIALIZER_TESTS(static, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(dynamic, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(runtime, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
DEFINE_UNION_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
DEFINE_UNION_TESTS(assigned_copy, ALWAYS_FAIL);
/* No initialization without compiler instrumentation. */
DEFINE_SCALAR_TESTS(none, STRONG_PASS);
DEFINE_STRUCT_TESTS(none, BYREF_PASS);
Expand Down Expand Up @@ -436,13 +523,23 @@ DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL);
KUNIT_CASE(test_trailing_hole_ ## init),\
KUNIT_CASE(test_packed_ ## init) \

#define KUNIT_test_unions(init) \
KUNIT_CASE(test_same_sizes_ ## init), \
KUNIT_CASE(test_small_start_ ## init), \
KUNIT_CASE(test_small_end_ ## init) \

static struct kunit_case stackinit_test_cases[] = {
/* These are explicitly initialized and should always pass. */
KUNIT_test_scalars(zero),
KUNIT_test_structs(zero),
KUNIT_test_structs(old_zero),
KUNIT_test_unions(zero),
KUNIT_test_unions(old_zero),
/* Padding here appears to be accidentally always initialized? */
KUNIT_test_structs(dynamic_partial),
KUNIT_test_structs(assigned_dynamic_partial),
KUNIT_test_unions(dynamic_partial),
KUNIT_test_unions(assigned_dynamic_partial),
/* Padding initialization depends on compiler behaviors. */
KUNIT_test_structs(static_partial),
KUNIT_test_structs(static_all),
Expand All @@ -452,8 +549,17 @@ static struct kunit_case stackinit_test_cases[] = {
KUNIT_test_structs(assigned_static_partial),
KUNIT_test_structs(assigned_static_all),
KUNIT_test_structs(assigned_dynamic_all),
KUNIT_test_unions(static_partial),
KUNIT_test_unions(static_all),
KUNIT_test_unions(dynamic_all),
KUNIT_test_unions(runtime_partial),
KUNIT_test_unions(runtime_all),
KUNIT_test_unions(assigned_static_partial),
KUNIT_test_unions(assigned_static_all),
KUNIT_test_unions(assigned_dynamic_all),
/* Everything fails this since it effectively performs a memcpy(). */
KUNIT_test_structs(assigned_copy),
KUNIT_test_unions(assigned_copy),
/* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
KUNIT_test_scalars(none),
KUNIT_CASE(test_switch_1_none),
Expand Down
3 changes: 3 additions & 0 deletions scripts/Makefile.extrawarn
View file
Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,9 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
# Warn if there is an enum types mismatch
KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion)

# Explicitly clear padding bits during variable initialization
KBUILD_CFLAGS += $(call cc-option,-fzero-init-padding-bits=all)

KBUILD_CFLAGS += -Wextra
KBUILD_CFLAGS += -Wunused

Expand Down

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