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kasan: test: bypass __alloc_size checks 

Intentional overflows, as performed by the KASAN tests, are detected at
compile time[1] (instead of only at run-time) with the addition of
__alloc_size.  Fix this by forcing the compiler into not being able to
trust the size used following the kmalloc()s.

[1] https://lore.kernel.org/lkml/20211005184717.65c6d8eb39350395e387b71f@linux-foundation.org

Link: https://lkml.kernel.org/r/20211006181544.1670992-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kees Cook 2021-11-05 13:36:12 -07:00 committed by Linus Torvalds
parent 8772716f96
commit d73dad4eb5
2 changed files with 9 additions and 1 deletions
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8
lib/test_kasan.c
View File

@ -440,6 +440,7 @@ static void kmalloc_oob_memset_2(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL); ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
OPTIMIZER_HIDE_VAR(size);
KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2)); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2));
kfree(ptr); kfree(ptr);
} }
@ -452,6 +453,7 @@ static void kmalloc_oob_memset_4(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL); ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
OPTIMIZER_HIDE_VAR(size);
KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4)); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4));
kfree(ptr); kfree(ptr);
} }
@ -464,6 +466,7 @@ static void kmalloc_oob_memset_8(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL); ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
OPTIMIZER_HIDE_VAR(size);
KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8)); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8));
kfree(ptr); kfree(ptr);
} }
@ -476,6 +479,7 @@ static void kmalloc_oob_memset_16(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL); ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
OPTIMIZER_HIDE_VAR(size);
KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16)); KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16));
kfree(ptr); kfree(ptr);
} }
@ -488,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL); ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
OPTIMIZER_HIDE_VAR(size);
KUNIT_EXPECT_KASAN_FAIL(test, KUNIT_EXPECT_KASAN_FAIL(test,
memset(ptr, 0, size + KASAN_GRANULE_SIZE)); memset(ptr, 0, size + KASAN_GRANULE_SIZE));
kfree(ptr); kfree(ptr);
@ -497,7 +502,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
{ {
char *ptr; char *ptr;
size_t size = 64; size_t size = 64;
volatile size_t invalid_size = -2; size_t invalid_size = -2;
/* /*
* Hardware tag-based mode doesn't check memmove for negative size. * Hardware tag-based mode doesn't check memmove for negative size.
@ -510,6 +515,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
memset((char *)ptr, 0, 64); memset((char *)ptr, 0, 64);
OPTIMIZER_HIDE_VAR(invalid_size);
KUNIT_EXPECT_KASAN_FAIL(test, KUNIT_EXPECT_KASAN_FAIL(test,
memmove((char *)ptr, (char *)ptr + 4, invalid_size)); memmove((char *)ptr, (char *)ptr + 4, invalid_size));
kfree(ptr); kfree(ptr);

2
lib/test_kasan_module.c
View File

@ -35,6 +35,8 @@ static noinline void __init copy_user_test(void)
return; return;
} }
OPTIMIZER_HIDE_VAR(size);
pr_info("out-of-bounds in copy_from_user()\n"); pr_info("out-of-bounds in copy_from_user()\n");
unused = copy_from_user(kmem, usermem, size + 1); unused = copy_from_user(kmem, usermem, size + 1);