From: Nico Pache <npache@redhat.com>
To: Marco Elver <elver@google.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Kees Cook <keescook@chromium.org>,
Brendan Higgins <brendanhiggins@google.com>,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE
Date: Mon, 24 Jan 2022 13:56:30 -0500 [thread overview]
Message-ID: <8f457c89-28ed-71d1-5afa-2386abec6da9@redhat.com> (raw)
In-Reply-To: <20220124160744.1244685-1-elver@google.com>
On 1/24/22 11:07, Marco Elver wrote:
> With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform
> dynamic checks using __builtin_object_size(ptr), which when failed will
> panic the kernel.
>
> Because the KASAN test deliberately performs out-of-bounds operations,
> the kernel panics with FORITY_SOURCE, for example:
>
> | kernel BUG at lib/string_helpers.c:910!
> | invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
> | CPU: 1 PID: 137 Comm: kunit_try_catch Tainted: G B 5.16.0-rc3+ #3
> | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
> | RIP: 0010:fortify_panic+0x19/0x1b
> | ...
> | Call Trace:
> | <TASK>
> | kmalloc_oob_in_memset.cold+0x16/0x16
> | ...
>
> Fix it by also hiding `ptr` from the optimizer, which will ensure that
> __builtin_object_size() does not return a valid size, preventing
> fortified string functions from panicking.
>
> Reported-by: Nico Pache <npache@redhat.com>
> Signed-off-by: Marco Elver <elver@google.com>
Looks good! Thanks for posting this Marco :)
Reviewed-by: Nico Pache <npache@redhat.com>
> ---
> lib/test_kasan.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 847cdbefab46..26a5c9007653 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -492,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test)
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(size);
> KUNIT_EXPECT_KASAN_FAIL(test,
> memset(ptr, 0, size + KASAN_GRANULE_SIZE));
> @@ -515,6 +516,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> memset((char *)ptr, 0, 64);
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(invalid_size);
> KUNIT_EXPECT_KASAN_FAIL(test,
> memmove((char *)ptr, (char *)ptr + 4, invalid_size));
> @@ -531,6 +533,7 @@ static void kmalloc_memmove_invalid_size(struct kunit *test)
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> memset((char *)ptr, 0, 64);
> + OPTIMIZER_HIDE_VAR(ptr);
> KUNIT_EXPECT_KASAN_FAIL(test,
> memmove((char *)ptr, (char *)ptr + 4, invalid_size));
> kfree(ptr);
> @@ -893,6 +896,7 @@ static void kasan_memchr(struct kunit *test)
> ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(size);
> KUNIT_EXPECT_KASAN_FAIL(test,
> kasan_ptr_result = memchr(ptr, '1', size + 1));
> @@ -919,6 +923,7 @@ static void kasan_memcmp(struct kunit *test)
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> memset(arr, 0, sizeof(arr));
>
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(size);
> KUNIT_EXPECT_KASAN_FAIL(test,
> kasan_int_result = memcmp(ptr, arr, size+1));
>
prev parent reply other threads:[~2022-01-24 18:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-24 16:07 [PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE Marco Elver
2022-01-24 17:54 ` Andrey Konovalov
2022-01-24 17:59 ` Marco Elver
2022-01-24 18:24 ` Kees Cook
2022-01-24 18:56 ` Nico Pache [this message]
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