linux-hardening - Re: [PATCH 06/10] x86/tdx: Mark message.str as nonstring

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Message-ID: <b4f08d43-c421-4e8d-9bbb-c954c4472f8a@intel.com>
Date: Thu, 6 Feb 2025 17:12:11 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Kees Cook <kees@...nel.org>, Andy Shevchenko <andy@...nel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>, linux-coco@...ts.linux.dev,
 Sathya Prakash <sathya.prakash@...adcom.com>,
 Sreekanth Reddy <sreekanth.reddy@...adcom.com>,
 Suganath Prabu Subramani <suganath-prabu.subramani@...adcom.com>,
 Kashyap Desai <kashyap.desai@...adcom.com>,
 Sumit Saxena <sumit.saxena@...adcom.com>,
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
 "Martin K. Petersen" <martin.petersen@...cle.com>,
 Nilesh Javali <njavali@...vell.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Alexey Dobriyan <adobriyan@...il.com>, Sven Eckelmann <sven@...fation.org>,
 Tadeusz Struk <tadeusz.struk@...aro.org>, kernel test robot <lkp@...el.com>,
 Erick Archer <erick.archer@...look.com>, Dmitry Antipov
 <dmantipov@...dex.ru>, Ryusuke Konishi <konishi.ryusuke@...il.com>,
 Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
 linux-kernel@...r.kernel.org, MPT-FusionLinux.pdl@...adcom.com,
 linux-scsi@...r.kernel.org, mpi3mr-linuxdrv.pdl@...adcom.com,
 GR-QLogic-Storage-Upstream@...vell.com, linux-hardening@...r.kernel.org,
 linux-nilfs@...r.kernel.org
Subject: Re: [PATCH 06/10] x86/tdx: Mark message.str as nonstring

On 2/6/25 17:00, Kees Cook wrote:
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -170,7 +170,7 @@ static void __noreturn tdx_panic(const char *msg)
>  		/* Define register order according to the GHCI */
>  		struct { u64 r14, r15, rbx, rdi, rsi, r8, r9, rdx; };
>  
> -		char str[64];
> +		char str[64] __nonstring;
>  	} message;

So, the patch itself makes sense. But it does end up looking kinda
funky. We call it a "str"ing and then annotate it as not a string.

It doesn't have to be done in this patch, but it does seem like we
should probably not be using 'char' and also shouldn't call it anything
close to "string". Maybe:

	u8 message[64] __nonstring;

In any case, feel free to carry the annotation in your tree:

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>