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Message-ID: <1533896581.5885.16.camel@gmx.de>
Subject: Re: [PATCH] x86, kdump: Fix efi=noruntime NULL pointer dereference
From:   Mike Galbraith <efault@gmx.de>
To:     Dave Young <dyoung@redhat.com>
Cc:     Baoquan He <bhe@redhat.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        lkml <linux-kernel@vger.kernel.org>
Date:   Fri, 10 Aug 2018 12:23:01 +0200
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         <20180810084501.GA11901@dhcp-128-65.nay.redhat.com>
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On Fri, 2018-08-10 at 16:45 +0800, Dave Young wrote:
> 
> BTW, this patch only fix the kexec load phase problem,  even if kexec
> load successfully with the fix, the 2nd kernel can not boot because efi
> memmap info is not correct and usable.

Hm.  I didn't do anything else with kexec, but did crashdump my box
both w/wo efi=noruntime.

> So we should go with some fix similar to below, and do the cleanup we
> mentioned with a separate patch later.

Ah, you mean the one I had _just_ built when I saw this :)

> Also user space kexec-tools need a similar patch to error out in case
> no runtime maps.  It would be good to fix both userspace and kernel
> load.
> 
> diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> index 7326078eaa7a..e34ba2f53cfb 100644
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -123,7 +123,7 @@ static int setup_efi_info_memmap(struct boot_params *params,
>  	struct efi_info *ei = &params->efi_info;
>  
>  	if (!efi_map_sz)
> -		return 0;
> +		return -EINVAL;
>  
>  	efi_runtime_map_copy(efi_map, efi_map_sz);
>  
> @@ -166,9 +166,10 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
>  {
>  	struct efi_info *current_ei = &boot_params.efi_info;
>  	struct efi_info *ei = &params->efi_info;
> +	int ret;
>  
>  	if (!current_ei->efi_memmap_size)
> -		return 0;
> +		return -EINVAL;
>  
>  	/*
>  	 * If 1:1 mapping is not enabled, second kernel can not setup EFI
> @@ -176,8 +177,8 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
>  	 * acpi_rsdp=<addr> on kernel command line to make second kernel boot
>  	 * without efi.
>  	 */
> -	if (efi_enabled(EFI_OLD_MEMMAP))
> -		return 0;
> +	if (efi_enabled(EFI_OLD_MEMMAP) || !efi_enabled(EFI_RUNTIME_SERVICES))
> +		return -ENODEV;
>  
>  	ei->efi_loader_signature = current_ei->efi_loader_signature;
>  	ei->efi_systab = current_ei->efi_systab;
> @@ -186,8 +187,10 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
>  	ei->efi_memdesc_version = current_ei->efi_memdesc_version;
>  	ei->efi_memdesc_size = efi_get_runtime_map_desc_size();
>  
> -	setup_efi_info_memmap(params, params_load_addr, efi_map_offset,
> +	ret = setup_efi_info_memmap(params, params_load_addr, efi_map_offset,
>  			      efi_map_sz);
> +	if (ret)
> +		return ret;
>  	prepare_add_efi_setup_data(params, params_load_addr,
>  				   efi_setup_data_offset);
>  	return 0;
> @@ -250,8 +253,10 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
>  
>  #ifdef CONFIG_EFI
>  	/* Setup EFI state */
> -	setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
> +	ret = setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
>  			efi_setup_data_offset);
> +	if (ret)
> +		return ret;
>  #endif
>  
>  	/* Setup EDD info */