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From: Kees Cook <keescook@chromium.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Masahiro Yamada <masahiroy@kernel.org>,
	linux-kbuild@vger.kernel.org,
	"Gustavo A . R . Silva" <gustavoars@kernel.org>,
	clang-built-linux@googlegroups.com,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH 4/5] Makefile: Enable -Warray-bounds
Date: Wed, 2 Feb 2022 19:03:39 -0800	[thread overview]
Message-ID: <202202021902.97BAE673@keescook> (raw)
In-Reply-To: <cbf0cf07-2350-ed23-f6be-b2686c6a0cea@roeck-us.net>

On Wed, Feb 02, 2022 at 03:33:11PM -0800, Guenter Roeck wrote:
> On 2/2/22 12:56, Kees Cook wrote:
> > On Wed, Feb 02, 2022 at 08:09:03AM -0800, Guenter Roeck wrote:
> > > xtensa:allmodconfig:
> > > --------------
> > > Error log:
> > > In file included from include/linux/uaccess.h:11,
> > >                   from include/linux/sched/task.h:11,
> > >                   from arch/xtensa/kernel/process.c:21:
> > > arch/xtensa/kernel/process.c: In function 'copy_thread':
> > > arch/xtensa/kernel/process.c:262:52: error: array subscript 53 is above array bounds of 'long unsigned int[16]'
> > 
> > I assume this is a weird cast. I will also check this one out.
> > 
> 
>                                 int callinc = (regs->areg[0] >> 30) & 3;
>                                 int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
>                                 put_user(regs->areg[caller_ars+1],
>                                          ^^^^^^^^^^^^^^^^^^^^^^^^
>                                          (unsigned __user*)(usp - 12));
> 
> I think the problem is that XCHAL_NUM_AREGS can be up to 64,
> but the size of struct pt_regs->areg[] is fixed to 16.

Yeah, that's what I found too. The comment about pt_regs::areg seems to
hint that things treat pt_regs differently. I've asked on the xtensa list:
https://lore.kernel.org/linux-hardening/202202021501.DA6594BFC@keescook/

-- 
Kees Cook

  reply	other threads:[~2022-02-03  3:03 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18  8:11 [PATCH 0/5] Enable -Warray-bounds and -Wzero-length-bounds Kees Cook
2021-08-18  8:11 ` [PATCH 1/5] stddef: Add flexible array union helper Kees Cook
2021-08-18  8:11 ` [PATCH 2/5] treewide: Replace open-coded flex arrays in unions Kees Cook
2021-08-18  9:56   ` Marc Kleine-Budde
2021-08-18 21:51     ` Kees Cook
2021-08-18  8:11 ` [PATCH 3/5] treewide: Replace 0-element memcpy() destinations with flexible arrays Kees Cook
2021-08-18  8:11 ` [PATCH 4/5] Makefile: Enable -Warray-bounds Kees Cook
2022-02-02 16:09   ` Guenter Roeck
2022-02-02 20:56     ` Kees Cook
2022-02-02 23:33       ` Guenter Roeck
2022-02-03  3:03         ` Kees Cook [this message]
2022-02-02 22:02     ` Kees Cook
2022-02-02 22:11     ` Kees Cook
2022-02-02 23:21       ` Guenter Roeck
2022-02-03  3:02         ` Kees Cook
2021-08-18  8:11 ` [PATCH 5/5] Makefile: Enable -Wzero-length-bounds Kees Cook
2021-08-25 21:17   ` Nick Desaulniers

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