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FROMLIST: lib: test_stackinit.c: XFAIL switch variable init tests

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The tests for initializing a variable defined between a switch
statement's test and its first "case" statement are currently not
initialized in Clang[1] nor the proposed auto-initialization feature in
GCC.

We should retain the test (so that we can evaluate compiler fixes),
but mark it as an "expected fail". The rest of the kernel source will
be adjusted to avoid this corner case.

Also disable -Wswitch-unreachable for the test so that the intentionally
broken code won't trigger warnings for GCC (nor future Clang) when
initialization happens this unhandled place.

[1] https://bugs.llvm.org/show_bug.cgi?id=44916

Suggested-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
[adelva: cherry picking to avoid boot test flakes]
Bug: 144999193
Link: https://lore.kernel.org/lkml/202002191358.2897A07C6@keescook/
Change-Id: I0e691f2299ab42526ea306a92551a1188c469136
Signed-off-by: Alistair Delva <adelva@google.com>
This commit is contained in:
Kees Cook 2020-02-19 14:02:32 -08:00 committed by Alistair Delva
parent 8290fa4ad8
commit 4052265b8b
2 changed files with 19 additions and 10 deletions
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1
lib/Makefile
View File

@ -84,6 +84,7 @@ obj-$(CONFIG_TEST_KMOD) += test_kmod.o
obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
obj-$(CONFIG_TEST_MEMCAT_P) += test_memcat_p.o
obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
CFLAGS_test_stackinit.o += $(call cc-disable-warning, switch-unreachable)
obj-$(CONFIG_TEST_STACKINIT) += test_stackinit.o
obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o

28
lib/test_stackinit.c
View File

@ -92,8 +92,9 @@ static bool range_contains(char *haystack_start, size_t haystack_size,
* @var_type: type to be tested for zeroing initialization
* @which: is this a SCALAR, STRING, or STRUCT type?
* @init_level: what kind of initialization is performed
* @xfail: is this test expected to fail?
*/
#define DEFINE_TEST_DRIVER(name, var_type, which) \
#define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
/* Returns 0 on success, 1 on failure. */ \
static noinline __init int test_ ## name (void) \
{ \
@ -139,13 +140,14 @@ static noinline __init int test_ ## name (void) \
for (sum = 0, i = 0; i < target_size; i++) \
sum += (check_buf[i] == 0xFF); \
\
if (sum == 0) \
if (sum == 0) { \
pr_info(#name " ok\n"); \
else \
pr_warn(#name " FAIL (uninit bytes: %d)\n", \
sum); \
\
return (sum != 0); \
return 0; \
} else { \
pr_warn(#name " %sFAIL (uninit bytes: %d)\n", \
(xfail) ? "X" : "", sum); \
return (xfail) ? 0 : 1; \
} \
}
#define DEFINE_TEST(name, var_type, which, init_level) \
/* no-op to force compiler into ignoring "uninitialized" vars */\
@ -189,7 +191,7 @@ static noinline __init int leaf_ ## name(unsigned long sp, \
\
return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
} \
DEFINE_TEST_DRIVER(name, var_type, which)
DEFINE_TEST_DRIVER(name, var_type, which, 0)
/* Structure with no padding. */
struct test_packed {
@ -326,8 +328,14 @@ static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
return __leaf_switch_none(2, fill);
}
DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR);
DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR);
/*
* These are expected to fail for most configurations because neither
* GCC nor Clang have a way to perform initialization of variables in
* non-code areas (i.e. in a switch statement before the first "case").
* https://bugs.llvm.org/show_bug.cgi?id=44916
*/
DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, 1);
DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, 1);
static int __init test_stackinit_init(void)
{