From: Arnd Bergmann <arnd@arndb.de>
To: Kees Cook <keescook@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lkdtm: fix maybe-uninitialized warning
Date: Tue, 26 Jul 2016 22:58:32 +0200 [thread overview]
Message-ID: <24917262.Z3gWB5hbbY@wuerfel> (raw)
In-Reply-To: <CAGXu5jJ+c2-x72P95DUcb-V6SKmhpbayW2gv=zu2vpF_R5ScVQ@mail.gmail.com>
On Tuesday, July 26, 2016 8:21:37 AM CEST Kees Cook wrote:
> On Tue, Jul 26, 2016 at 5:28 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > The do_usercopy_stack() function uses uninitialized stack data to initialize
> > more of the stack, which causes a warning in some configurations (ARM allmodconfig):
> >
> > drivers/misc/lkdtm_usercopy.c:52:15: warning: 'bad_stack' may be used uninitialized in this function [-Wmaybe-uninitialized]
> >
> > The warning gets reports by Mark Brown's build bot and looks correct (we are trying
> > to trick the compiler here, and sometimes the compiler notices), and I could reproduce
> > it with gcc-4.7 through gcc-5.3 but not gcc-6.1 for some reason.
> >
> > This changes the code to use the low byte of the address of the stack to initialize
> > the stack data, instead of using data from the stack itself, to avoid the warning.
> >
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > Fixes: a3dff71c1c88 ("lkdtm: split usercopy tests to separate file")
>
> Acked-by: Kees Cook <keescook@chromium.org>
>
> I thought I already sent this fix to Greg?
Possible. I mentioned the problem to you when it first showed up,
but noticed today that I didn't have a patch for it in my testing
tree (since I test with gcc-6.1, which doesn't show the bug).
> Maybe it got lost...
More likely that it's still in his backlog then.
Arnd
prev parent reply other threads:[~2016-07-26 20:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-26 12:28 Arnd Bergmann
2016-07-26 15:21 ` Kees Cook
2016-07-26 20:58 ` Arnd Bergmann [this message]
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