From: Andrey Konovalov <andreyknvl@google.com>
To: Marco Elver <elver@google.com>
Cc: Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
kasan-dev <kasan-dev@googlegroups.com>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Dmitry Vyukov <dvyukov@google.com>,
clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH] lkdtm: disable KASAN for rodata.o
Date: Tue, 15 Dec 2020 15:00:52 +0100 [thread overview]
Message-ID: <CAAeHK+x3w=rw3Jk3Zg-Q2H6iboWH3dqGvgm9ZXxsCaBGGzR9JA@mail.gmail.com> (raw)
In-Reply-To: <20201214191413.3164796-1-elver@google.com>
On Mon, Dec 14, 2020 at 8:15 PM Marco Elver <elver@google.com> wrote:
>
> Building lkdtm with KASAN and Clang 11 or later results in the following
> error when attempting to load the module:
>
> kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
> BUG: unable to handle page fault for address: ffffffffc019cd70
> #PF: supervisor instruction fetch in kernel mode
> #PF: error_code(0x0011) - permissions violation
> ...
> RIP: 0010:asan.module_ctor+0x0/0xffffffffffffa290 [lkdtm]
> ...
> Call Trace:
> do_init_module+0x17c/0x570
> load_module+0xadee/0xd0b0
> __x64_sys_finit_module+0x16c/0x1a0
> do_syscall_64+0x34/0x50
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> The reason is that rodata.o generates a dummy function that lives in
> .rodata to validate that .rodata can't be executed; however, Clang 11
> adds KASAN globals support by generating module constructors to
> initialize globals redzones. When Clang 11 adds a module constructor to
> rodata.o, it is also added to .rodata: any attempt to call it on
> initialization results in the above error.
>
> Therefore, disable KASAN instrumentation for rodata.o.
>
> Signed-off-by: Marco Elver <elver@google.com>
> ---
> drivers/misc/lkdtm/Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
> index c70b3822013f..1c4c7aca0026 100644
> --- a/drivers/misc/lkdtm/Makefile
> +++ b/drivers/misc/lkdtm/Makefile
> @@ -11,6 +11,7 @@ lkdtm-$(CONFIG_LKDTM) += usercopy.o
> lkdtm-$(CONFIG_LKDTM) += stackleak.o
> lkdtm-$(CONFIG_LKDTM) += cfi.o
>
> +KASAN_SANITIZE_rodata.o := n
> KASAN_SANITIZE_stackleak.o := n
> KCOV_INSTRUMENT_rodata.o := n
>
>
> base-commit: 2c85ebc57b3e1817b6ce1a6b703928e113a90442
> --
> 2.29.2.684.gfbc64c5ab5-goog
>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Thanks for taking care of this!
prev parent reply other threads:[~2020-12-15 14:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-14 19:14 [PATCH] lkdtm: disable KASAN for rodata.o Marco Elver
2020-12-15 14:00 ` Andrey Konovalov [this message]
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