Messages in this thread | | | Subject | Re: [PATCH 1/2] kasan: test: use underlying string helpers | From | Vincenzo Frascino <> | Date | Thu, 14 Oct 2021 10:12:54 +0200 |
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On 10/13/21 5:00 PM, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > Calling memcmp() and memchr() with an intentional buffer overflow > is now caught at compile time: > > In function 'memcmp', > inlined from 'kasan_memcmp' at lib/test_kasan.c:897:2: > include/linux/fortify-string.h:263:25: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter) > 263 | __read_overflow(); > | ^~~~~~~~~~~~~~~~~ > In function 'memchr', > inlined from 'kasan_memchr' at lib/test_kasan.c:872:2: > include/linux/fortify-string.h:277:17: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter) > 277 | __read_overflow(); > | ^~~~~~~~~~~~~~~~~ > > Change the kasan tests to wrap those inside of a noinline function > to prevent the compiler from noticing the bug and let kasan find > it at runtime. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> --- > lib/test_kasan.c | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > > diff --git a/lib/test_kasan.c b/lib/test_kasan.c > index 67ed689a0b1b..903215e944f1 100644 > --- a/lib/test_kasan.c > +++ b/lib/test_kasan.c > @@ -852,6 +852,21 @@ static void kmem_cache_invalid_free(struct kunit *test) > kmem_cache_destroy(cache); > } > > +/* > + * noinline wrappers to prevent the compiler from noticing the overflow > + * at compile time rather than having kasan catch it. > + * */ > +static noinline void *__kasan_memchr(const void *s, int c, size_t n) > +{ > + return memchr(s, c, n); > +} > + > +static noinline int __kasan_memcmp(const void *s1, const void *s2, size_t n) > +{ > + return memcmp(s1, s2, n); > +} > + > + > static void kasan_memchr(struct kunit *test) > { > char *ptr; > @@ -870,7 +885,7 @@ static void kasan_memchr(struct kunit *test) > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); > > KUNIT_EXPECT_KASAN_FAIL(test, > - kasan_ptr_result = memchr(ptr, '1', size + 1)); > + kasan_ptr_result = __kasan_memchr(ptr, '1', size + 1)); > > kfree(ptr); > } > @@ -895,7 +910,7 @@ static void kasan_memcmp(struct kunit *test) > memset(arr, 0, sizeof(arr)); > > KUNIT_EXPECT_KASAN_FAIL(test, > - kasan_int_result = memcmp(ptr, arr, size+1)); > + kasan_int_result = __kasan_memcmp(ptr, arr, size+1)); > kfree(ptr); > } > >
-- Regards, Vincenzo
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