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SubjectRe: [PATCH] x86, kdump: Fix efi=noruntime NULL pointer dereference
Hi Mike,

Thanks for the patch!
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.

At first glance, efi_get_runtime_map_size should return 0 in case
noruntime.

Also since we are here, would you mind to restructure the bzImage64_load
function, and try to move all efi related code to setup_efi_state()?


setup_boot_parameters(struct kimage *image, struct boot_params *params,
unsigned long params_load_addr,
unsigned int efi_map_offset, unsigned int efi_map_sz,
unsigned int efi_setup_data_offset)
{
[snip]

#ifdef CONFIG_EFI
/* Setup EFI state */
setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
efi_setup_data_offset);
#endif

[snip]
}

Currently bzImage64_load prepares the efi_map_offset, efi_map_sz,
and efi_setup_data_offset and then pass it to setup_boot_parameters and
setup_efi_state. It should be better to move those efi_* variables to
setup_efi_state().

So we can call setup_efi_state only when efi runtime is enabled.

>
> 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;

Thanks
Dave

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