linux-kernel - Re: [PATCH] x86/kexec: fix incorrect end address passed to kernel_ident_mapping

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Date: Thu, 21 Dec 2023 14:03:00 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Yuntao Wang <ytcoode@...il.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, Baoquan He
 <bhe@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
 <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
 <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, Simon
 Horman <horms@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] x86/kexec: fix incorrect end address passed to
 kernel_ident_mapping_init()

On Thu, 21 Dec 2023 18:17:02 +0800 Yuntao Wang <ytcoode@...il.com> wrote:

> kernel_ident_mapping_init() takes an exclusive memory range [pstart, pend)
> where pend is not included in the range, while res represents an inclusive
> memory range [start, end] where end is considered part of the range.
> 
> Therefore, passing res->end directly to kernel_ident_mapping_init() is
> incorrect, the correct end address should be `res->end + 1`.
> 
> ...
>
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -44,7 +44,7 @@ static int mem_region_callback(struct resource *res, void *arg)
>  	struct init_pgtable_data *data = arg;
>  
>  	return kernel_ident_mapping_init(data->info, data->level4p,
> -					 res->start, res->end);
> +					 res->start, res->end + 1);
>  }

Thanks.  When fixing a bug, please always full describe the
userspace-visible effects of that bug.

In this case I'm assuming "none", due to kernel_ident_mapping_init()'s
upward rounding of the address?