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

[Mike Galbraith]

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 <efa...@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;