From: "H. Peter Anvin" <hpa@zytor.com>
To: Kees Cook <keescook@chromium.org>, Guenter Roeck <linux@roeck-us.net>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] gcc4: Disable __compiletime_object_size for GCC 4.6+
Date: Wed, 13 Nov 2013 12:57:13 -0800 [thread overview]
Message-ID: <5283E7A9.6090706@zytor.com> (raw)
In-Reply-To: <20131113183913.GK4994@outflux.net>
On 11/13/2013 10:39 AM, Kees Cook wrote:
> Hi Guenter,
>
> On Fri, Apr 12, 2013 at 07:49:08PM -0700, Guenter Roeck wrote:
>> __builtin_object_size is known to be broken on gcc 4.6+.
>> See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48880 for details.
>>
>> This causes unnecssary build warnings and errors such as
>>
>> In function 'copy_from_user', inlined from 'sb16_copy_from_user'
>> at sound/oss/sb_audio.c:878:22:
>> arch/x86/include/asm/uaccess_32.h:211:26: error: call to 'copy_from_user_overflow'
>> declared with attribute error: copy_from_user() buffer size is not provably correct
>> make[3]: [sound/oss/sb_audio.o] Error 1 (ignored)
>>
>> Disable it where broken.
>
> Is there an alternative? This means that things like
> DEBUG_STRICT_USER_COPY_CHECKS are being rendered useless. I don't think
> this is _always_ broken, just under certain situations, right?
>
It would be one thing to block it for, say, gcc 4.6 and 4.7 only, but
without an upper cap I don't think this is at all okay.
-hpa
next prev parent reply other threads:[~2013-11-13 20:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-13 2:49 [PATCH] gcc4: Disable __compiletime_object_size for GCC 4.6+ Guenter Roeck
2013-11-13 18:39 ` Kees Cook
2013-11-13 20:24 ` Guenter Roeck
2013-11-13 20:57 ` H. Peter Anvin [this message]
2013-11-14 1:19 ` Guenter Roeck
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