linux-kernel - Re: [PATCH] [v2] ubsan: build ubsan.c more conservatively

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Date:   Mon, 22 Jul 2019 15:56:48 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Arnd Bergmann <arnd@...db.de>, akpm@...ux-foundation.org
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, stable@...r.kernel.org,
        Borislav Petkov <bp@...en8.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] [v2] ubsan: build ubsan.c more conservatively



On 7/22/19 3:50 PM, Arnd Bergmann wrote:
> objtool points out several conditions that it does not like, depending
> on the combination with other configuration options and compiler
> variants:
> 
> stack protector:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0xbf: call to __stack_chk_fail() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0xbe: call to __stack_chk_fail() with UACCESS enabled
> 
> stackleak plugin:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x4a: call to stackleak_track_stack() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x4a: call to stackleak_track_stack() with UACCESS enabled
> 
> kasan:
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch()+0x25: call to memcpy() with UACCESS enabled
> lib/ubsan.o: warning: objtool: __ubsan_handle_type_mismatch_v1()+0x25: call to memcpy() with UACCESS enabled
> 
> The stackleak and kasan options just need to be disabled for this file
> as we do for other files already. For the stack protector, we already
> attempt to disable it, but this fails on clang because the check is
> mixed with the gcc specific -fno-conserve-stack option. According
> to Andrey Ryabinin, that option is not even needed, dropping it here
> fixes the stackprotector issue.
> 
> Fixes: d08965a27e84 ("x86/uaccess, ubsan: Fix UBSAN vs. SMAP")
> Link: https://lore.kernel.org/lkml/20190617123109.667090-1-arnd@arndb.de/t/
> Link: https://lore.kernel.org/lkml/20190722091050.2188664-1-arnd@arndb.de/t/
> Cc: stable@...r.kernel.org
> Signed-off-by: Arnd Bergmann <arnd@...db.de>


Reviewed-by: Andrey Ryabinin <aryabinin@...tuozzo.com>