linux-kernel - Re: [PATCH v4 6/7] x86/crash: pass dm crypt keys to kdump kernel

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Date: Fri, 7 Jun 2024 17:57:38 +0800
From: Baoquan He <bhe@...hat.com>
To: Coiby Xu <coxu@...hat.com>
Cc: kexec@...ts.infradead.org, Ondrej Kozina <okozina@...hat.com>,
	Milan Broz <gmazyland@...il.com>,
	Thomas Staudt <tstaudt@...ibm.com>,
	Daniel P . Berrangé <berrange@...hat.com>,
	Kairui Song <ryncsn@...il.com>,
	Jan Pazdziora <jpazdziora@...hat.com>,
	Pingfan Liu <kernelfans@...il.com>, Dave Young <dyoung@...hat.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Dave Hansen <dave.hansen@...el.com>,
	Vitaly Kuznetsov <vkuznets@...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>
Subject: Re: [PATCH v4 6/7] x86/crash: pass dm crypt keys to kdump kernel

On 05/23/24 at 01:04pm, Coiby Xu wrote:
> 1st kernel will build up the kernel command parameter dmcryptkeys as
> similar to elfcorehdr to pass the memory address of the stored info of
> dm crypt key to kdump kernel.
> 
> Signed-off-by: Coiby Xu <coxu@...hat.com>
> ---
>  arch/x86/kernel/crash.c           | 15 ++++++++++++++-
>  arch/x86/kernel/kexec-bzimage64.c |  7 +++++++
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index f06501445cd9..74b3844ae53c 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -266,6 +266,7 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
>  				 unsigned long long mend)
>  {
>  	unsigned long start, end;
> +	int r;
            ~?

r is only to contain the returned value? Then you can call it ret as
many do in kernel code.

>  
>  	cmem->ranges[0].start = mstart;
>  	cmem->ranges[0].end = mend;
> @@ -274,7 +275,19 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
>  	/* Exclude elf header region */
>  	start = image->elf_load_addr;
>  	end = start + image->elf_headers_sz - 1;
> -	return crash_exclude_mem_range(cmem, start, end);
> +	r = crash_exclude_mem_range(cmem, start, end);
> +
> +	if (r)
> +		return r;
> +
> +	/* Exclude dm crypt keys region */
> +	if (image->dm_crypt_keys_addr) {
> +		start = image->dm_crypt_keys_addr;
> +		end = start + image->dm_crypt_keys_sz - 1;
> +		return crash_exclude_mem_range(cmem, start, end);
> +	}

You need adjust the array length of cmem->ranges[], I believe you will
cause the array overflow because the keys are randomly set and mostly
will be in the middle of crashkernel region.

> +
> +	return r;
>  }
>  
>  /* Prepare memory map for crash dump kernel */