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kunit/fortify: Fix replaced failure path to unbreak __alloc_size

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The __alloc_size annotation for kmemdup() was getting disabled under
KUnit testing because the replaced fortify_panic macro implementation
was using "return NULL" as a way to survive the sanity checking. But
having the chance to return NULL invalidated __alloc_size, so kmemdup
was not passing the __builtin_dynamic_object_size() tests any more:

[23:26:18] [PASSED] fortify_test_alloc_size_kmalloc_const
[23:26:19]     # fortify_test_alloc_size_kmalloc_dynamic: EXPECTATION FAILED at lib/fortify_kunit.c:265
[23:26:19]     Expected __builtin_dynamic_object_size(p, 1) == expected, but
[23:26:19]         __builtin_dynamic_object_size(p, 1) == -1 (0xffffffffffffffff)
[23:26:19]         expected == 11 (0xb)
[23:26:19] __alloc_size() not working with __bdos on kmemdup("hello there", len, gfp)
[23:26:19] [FAILED] fortify_test_alloc_size_kmalloc_dynamic

Normal builds were not affected: __alloc_size continued to work there.

Use a zero-sized allocation instead, which allows __alloc_size to
behave.

Fixes: 4ce615e798 ("fortify: Provide KUnit counters for failure testing")
Fixes: fa4a3f86d4 ("fortify: Add KUnit tests for runtime overflows")
Link: https://lore.kernel.org/r/20240501232937.work.532-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2024-05-01 16:29:48 -07:00
parent a284e43852
commit 74df22453c
2 changed files with 5 additions and 4 deletions
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3
include/linux/fortify-string.h
View file

@ -738,7 +738,8 @@ __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp
if (__compiletime_lessthan(p_size, size))
__read_overflow();
if (p_size < size)
fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ, p_size, size, NULL);
fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ, p_size, size,
__real_kmemdup(p, 0, gfp));
return __real_kmemdup(p, size, gfp);
}

6
lib/fortify_kunit.c
View file

@ -1002,19 +1002,19 @@ static void fortify_test_kmemdup(struct kunit *test)
/* Out of bounds by 1 byte. */
copy = kmemdup(src, len + 1, GFP_KERNEL);
KUNIT_EXPECT_NULL(test, copy);
KUNIT_EXPECT_PTR_EQ(test, copy, ZERO_SIZE_PTR);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 1);
kfree(copy);
/* Way out of bounds. */
copy = kmemdup(src, len * 2, GFP_KERNEL);
KUNIT_EXPECT_NULL(test, copy);
KUNIT_EXPECT_PTR_EQ(test, copy, ZERO_SIZE_PTR);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 2);
kfree(copy);
/* Starting offset causing out of bounds. */
copy = kmemdup(src + 1, len, GFP_KERNEL);
KUNIT_EXPECT_NULL(test, copy);
KUNIT_EXPECT_PTR_EQ(test, copy, ZERO_SIZE_PTR);
KUNIT_EXPECT_EQ(test, fortify_read_overflows, 3);
kfree(copy);
}