linux-kernel - Re: [PATCH v4 0/4] Introduce the initify gcc plugin

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Date:   Thu, 12 Jan 2017 15:40:41 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Emese Revfy <re.emese@...il.com>
Cc:     "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Josh Triplett <josh@...htriplett.org>,
        PaX Team <pageexec@...email.hu>,
        Brad Spengler <spender@...ecurity.net>,
        Michal Marek <mmarek@...e.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-kbuild <linux-kbuild@...r.kernel.org>, minipli@...linux.so,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        David Brown <david.brown@...aro.org>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v4 0/4] Introduce the initify gcc plugin

On Thu, Jan 12, 2017 at 3:27 PM, Kees Cook <keescook@...omium.org> wrote:
> On Thu, Jan 12, 2017 at 1:41 PM, Emese Revfy <re.emese@...il.com> wrote:
>> On Tue, 10 Jan 2017 17:09:31 -0800
>> Kees Cook <keescook@...omium.org> wrote:
>>
>>> WARNING: vmlinux.o(.text+0x1087e7): Section mismatch in reference from
>>> the function rebind_subsystems() to the variable
>>> .init.rodata.str:__func__.4400
>>> The function rebind_subsystems() references
>>> the variable __initconst __func__.4400.
>>> This is often because rebind_subsystems lacks a __initconst
>>> annotation or the annotation of __func__.4400 is wrong.
>>
>> Thanks for the report, you can find the fix here:
>> https://github.com/ephox-gcc-plugins/initify/commit/25f34834e3373e067133bc5d39d42c50a3592d56
>
> Awesome! I can confirm, it builds without warnings now. Thanks!

Hm, actually, with an "allyesconfig" build, I'm still seeing warnings
(and possibly some nocapture verification failures).

Most look like this:

WARNING: drivers/clk/bcm/built-in.o(.text+0xec2): Section mismatch in
reference from the function clk_gate() to the variable
.init.rodata.str:__func__.29708
The function clk_gate() references
the variable __initconst __func__.29708.
This is often because clk_gate lacks a __initconst
annotation or the annotation of __func__.29708 is wrong.

And there's this (should KASAN be disabled for initify?)

mm/kasan/kasan.c: In function ‘memmove’:
mm/kasan/kasan.c:346:7: warning: ‘memmove’ captures its 2 (‘src’)
parameter, please remove it from the nocapture attribute.
 void *memmove(void *dest, const void *src, size_t len)
       ^
mm/kasan/kasan.c: In function ‘memcpy’:
mm/kasan/kasan.c:355:7: warning: ‘memcpy’ captures its 2 (‘src’)
parameter, please remove it from the nocapture attribute.
 void *memcpy(void *dest, const void *src, size_t len)
       ^

And ACPI:

drivers/acpi/acpica/utdebug.c: In function ‘acpi_debug_print’:
drivers/acpi/acpica/utdebug.c:158:1: warning: ‘acpi_debug_print’
captures its 3 (‘function_name’) parameter, please remove it from the
nocapture attribute.
 acpi_debug_print(u32 requested_debug_level,
 ^


I used my initify v5 development tree, with the following patch, with
"make allyesconfig":

http://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/log/?h=for-next/gcc-plugin/initify

diff --git a/arch/Kconfig b/arch/Kconfig
index b6009a21ebea..5693ef5f22c8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -359,7 +359,6 @@ config HAVE_GCC_PLUGINS
 menuconfig GCC_PLUGINS
        bool "GCC plugins"
        depends on HAVE_GCC_PLUGINS
-       depends on !COMPILE_TEST
        help
          GCC plugins are loadable modules that provide extra features to the
          compiler. They are useful for runtime instrumentation and
static analysis.
@@ -429,6 +428,7 @@ config GCC_PLUGIN_INITIFY
 config GCC_PLUGIN_INITIFY_VERBOSE
        bool "Report initification"
        depends on GCC_PLUGIN_INITIFY
+       depends on !COMPILE_TEST
        help
          Print all initified strings and all functions which should be
          __init/__exit.


I'll see if acpi needs __noverified_nocapture ...

-Kees

-- 
Kees Cook
Nexus Security