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Date:   Fri, 10 Aug 2018 18:28:46 +0800
From:   Dave Young <dyoung@redhat.com>
To:     Mike Galbraith <efault@gmx.de>
Cc:     Baoquan He <bhe@redhat.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86, kdump: Fix efi=noruntime NULL pointer dereference
Message-ID: <20180810102846.GA31327@dhcp-128-65.nay.redhat.com>
References: <1533737025.4936.3.camel@gmx.de>
 <20180810084501.GA11901@dhcp-128-65.nay.redhat.com>
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On 08/10/18 at 04:45pm, Dave Young wrote:
> On 08/08/18 at 04:03pm, Mike Galbraith wrote:
> > When booting with efi=noruntime, we call efi_runtime_map_copy() while
> > loading the kdump kernel, and trip over a NULL efi.memmap.map.  Avoid
> > that and a useless allocation when the only mapping we can use (1:1)
> > is not available.
> > 
> > Signed-off-by: Mike Galbraith <efault@gmx.de>
> > ---
> >  arch/x86/kernel/kexec-bzimage64.c |   22 +++++++++++-----------
> >  1 file changed, 11 insertions(+), 11 deletions(-)
> > 
> > --- a/arch/x86/kernel/kexec-bzimage64.c
> > +++ b/arch/x86/kernel/kexec-bzimage64.c
> > @@ -122,9 +122,6 @@ static int setup_efi_info_memmap(struct
> >  	unsigned long efi_map_phys_addr = params_load_addr + efi_map_offset;
> >  	struct efi_info *ei = &params->efi_info;
> >  
> > -	if (!efi_map_sz)
> > -		return 0;
> > -
> >  	efi_runtime_map_copy(efi_map, efi_map_sz);
> >  
> >  	ei->efi_memmap = efi_map_phys_addr & 0xffffffff;
> > @@ -176,7 +173,7 @@ setup_efi_state(struct boot_params *para
> >  	 * acpi_rsdp=<addr> on kernel command line to make second kernel boot
> >  	 * without efi.
> >  	 */
> > -	if (efi_enabled(EFI_OLD_MEMMAP))
> > +	if (efi_enabled(EFI_OLD_MEMMAP) || !efi_enabled(EFI_MEMMAP))
> >  		return 0;
> >  
> >  	ei->efi_loader_signature = current_ei->efi_loader_signature;
> > @@ -338,7 +335,7 @@ static void *bzImage64_load(struct kimag
> >  	struct kexec_entry64_regs regs64;
> >  	void *stack;
> >  	unsigned int setup_hdr_offset = offsetof(struct boot_params, hdr);
> > -	unsigned int efi_map_offset, efi_map_sz, efi_setup_data_offset;
> > +	unsigned int efi_map_offset = 0, efi_map_sz = 0, efi_setup_data_offset = 0;
> >  	struct kexec_buf kbuf = { .image = image, .buf_max = ULONG_MAX,
> >  				  .top_down = true };
> >  	struct kexec_buf pbuf = { .image = image, .buf_min = MIN_PURGATORY_ADDR,
> > @@ -397,19 +394,22 @@ static void *bzImage64_load(struct kimag
> >  	 * have to create separate segment for each. Keeps things
> >  	 * little bit simple
> >  	 */
> > -	efi_map_sz = efi_get_runtime_map_size();
> >  	params_cmdline_sz = sizeof(struct boot_params) + cmdline_len +
> >  				MAX_ELFCOREHDR_STR_LEN;
> >  	params_cmdline_sz = ALIGN(params_cmdline_sz, 16);
> > -	kbuf.bufsz = params_cmdline_sz + ALIGN(efi_map_sz, 16) +
> > -				sizeof(struct setup_data) +
> > -				sizeof(struct efi_setup_data);
> > +	kbuf.bufsz = params_cmdline_sz + sizeof(struct setup_data);
> > +
> > +	/* Now add space for the efi stuff if we have a useable 1:1 mapping. */
> > +	if (!efi_enabled(EFI_OLD_MEMMAP) && efi_enabled(EFI_MEMMAP)) {
> > +		efi_map_sz = efi_get_runtime_map_size();
> > +		kbuf.bufsz += ALIGN(efi_map_sz, 16) + sizeof(struct efi_setup_data);
> > +		efi_map_offset = params_cmdline_sz;
> > +		efi_setup_data_offset = efi_map_offset + ALIGN(efi_map_sz, 16);
> > +	}
> >  
> >  	params = kzalloc(kbuf.bufsz, GFP_KERNEL);
> >  	if (!params)
> >  		return ERR_PTR(-ENOMEM);
> > -	efi_map_offset = params_cmdline_sz;
> > -	efi_setup_data_offset = efi_map_offset + ALIGN(efi_map_sz, 16);
> >  
> >  	/* Copy setup header onto bootparams. Documentation/x86/boot.txt */
> >  	setup_header_size = 0x0202 + kernel[0x0201] - setup_hdr_offset;
> 
> 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.
> 
> So we should go with some fix similar to below, and do the cleanup we
> mentioned with a separate patch later.
> 
> 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)

Here should check efi_enabled(EFI_BOOT) && ret

In case efi boot we need the efi info set correctly,  or one need pass
acpi_rsdp= in kernel cmdline param.

Still not sure how to allow one to workaround it by using acpi_rsdp=
param with kexec_file_load.. 


> +		return ret;
>  #endif
>  
>  	/* Setup EDD info */