efi: Fix handling of multiple efi_fake_mem= entries

Dave noticed that when specifying multiple efi_fake_mem= entries only
the last entry was successfully being reflected in the efi memory map.
This is due to the fact that the efi_memmap_insert() is being called
multiple times, but on successive invocations the insertion should be
applied to the last new memmap rather than the original map at
efi_fake_memmap() entry.

Rework efi_fake_memmap() to install the new memory map after each
efi_fake_mem= entry is parsed.

This also fixes an issue in efi_fake_memmap() that caused it to litter
emtpy entries into the end of the efi memory map. An empty entry causes
efi_memmap_insert() to attempt more memmap splits / copies than
efi_memmap_split_count() accounted for when sizing the new map. When
that happens efi_memmap_insert() may overrun its allocation, and if you
are lucky will spill over to an unmapped page leading to crash
signature like the following rather than silent corruption:

    BUG: unable to handle page fault for address: ffffffffff281000
    [..]
    RIP: 0010:efi_memmap_insert+0x11d/0x191
    [..]
    Call Trace:
     ? bgrt_init+0xbe/0xbe
     ? efi_arch_mem_reserve+0x1cb/0x228
     ? acpi_parse_bgrt+0xa/0xd
     ? acpi_table_parse+0x86/0xb8
     ? acpi_boot_init+0x494/0x4e3
     ? acpi_parse_x2apic+0x87/0x87
     ? setup_acpi_sci+0xa2/0xa2
     ? setup_arch+0x8db/0x9e1
     ? start_kernel+0x6a/0x547
     ? secondary_startup_64+0xb6/0xc0

Commit af1648984828 "x86/efi: Update e820 with reserved EFI boot
services data to fix kexec breakage" introduced more occurrences where
efi_memmap_insert() is invoked after an efi_fake_mem= configuration has
been parsed. Previously the side effects of vestigial empty entries were
benign, but with commit af1648984828 that follow-on efi_memmap_insert()
invocation triggers efi_memmap_insert() overruns.

Reported-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20191231014630.GA24942@dhcp-128-65.nay.redhat.com
Link: https://lore.kernel.org/r/20200113172245.27925-14-ardb@kernel.org

diff --git a/drivers/firmware/efi/fake_mem.c b/drivers/firmware/efi/fake_mem.c
index a8d2056..6e0f34a 100644 (file)
--- a/drivers/firmware/efi/fake_mem.c
+++ b/drivers/firmware/efi/fake_mem.c
@@ -34,25 +34,16 @@ static int __init cmp_fake_mem(const void *x1, const void *x2)
        return 0;
 }
 
-void __init efi_fake_memmap(void)
+static void __init efi_fake_range(struct efi_mem_range *efi_range)
 {
        struct efi_memory_map_data data = { 0 };
        int new_nr_map = efi.memmap.nr_map;
        efi_memory_desc_t *md;
        void *new_memmap;
-       int i;
-
-       if (!efi_enabled(EFI_MEMMAP) || !nr_fake_mem)
-               return;
 
        /* count up the number of EFI memory descriptor */
-       for (i = 0; i < nr_fake_mem; i++) {
-               for_each_efi_memory_desc(md) {
-                       struct range *r = &efi_fake_mems[i].range;
-
-                       new_nr_map += efi_memmap_split_count(md, r);
-               }
-       }
+       for_each_efi_memory_desc(md)
+               new_nr_map += efi_memmap_split_count(md, &efi_range->range);
 
        /* allocate memory for new EFI memmap */
        if (efi_memmap_alloc(new_nr_map, &data) != 0)
@@ -61,17 +52,27 @@ void __init efi_fake_memmap(void)
        /* create new EFI memmap */
        new_memmap = early_memremap(data.phys_map, data.size);
        if (!new_memmap) {
-               memblock_free(data.phys_map, data.size);
+               __efi_memmap_free(data.phys_map, data.size, data.flags);
                return;
        }
 
-       for (i = 0; i < nr_fake_mem; i++)
-               efi_memmap_insert(&efi.memmap, new_memmap, &efi_fake_mems[i]);
+       efi_memmap_insert(&efi.memmap, new_memmap, efi_range);
 
        /* swap into new EFI memmap */
        early_memunmap(new_memmap, data.size);
 
        efi_memmap_install(&data);
+}
+
+void __init efi_fake_memmap(void)
+{
+       int i;
+
+       if (!efi_enabled(EFI_MEMMAP) || !nr_fake_mem)
+               return;
+
+       for (i = 0; i < nr_fake_mem; i++)
+               efi_fake_range(&efi_fake_mems[i]);
 
        /* print new EFI memmap */
        efi_print_memmap();

diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
index 5016721..2ff1883 100644 (file)
--- a/drivers/firmware/efi/memmap.c
+++ b/drivers/firmware/efi/memmap.c
@@ -29,7 +29,7 @@ static phys_addr_t __init __efi_memmap_alloc_late(unsigned long size)
        return PFN_PHYS(page_to_pfn(p));
 }
 
-static void __init __efi_memmap_free(u64 phys, unsigned long size, unsigned long flags)
+void __init __efi_memmap_free(u64 phys, unsigned long size, unsigned long flags)
 {
        if (flags & EFI_MEMMAP_MEMBLOCK) {
                if (slab_is_available())

diff --git a/include/linux/efi.h b/include/linux/efi.h
index adbe421..7efd707 100644 (file)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -976,6 +976,8 @@ extern void __iomem *efi_lookup_mapped_addr(u64 phys_addr);
 
 extern int __init efi_memmap_alloc(unsigned int num_entries,
                                   struct efi_memory_map_data *data);
+extern void __efi_memmap_free(u64 phys, unsigned long size,
+                             unsigned long flags);
 extern int __init efi_memmap_init_early(struct efi_memory_map_data *data);
 extern int __init efi_memmap_init_late(phys_addr_t addr, unsigned long size);
 extern void __init efi_memmap_unmap(void);