From: Dan Williams <dan.j.williams@xxxxxxxxx>
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.
Link: https://lore.kernel.org/r/20191231014630.GA24942@xxxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: Dave Young <dyoung@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
drivers/firmware/efi/fake_mem.c | 31 ++++++++++++++++---------------
drivers/firmware/efi/memmap.c | 2 +-
include/linux/efi.h | 2 ++
3 files changed, 19 insertions(+), 16 deletions(-)
diff --git a/drivers/firmware/efi/fake_mem.c b/drivers/firmware/efi/fake_mem.c
index a8d20568d532..6e0f34a38171 100644
--- 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 501672166502..2ff1883dc788 100644
--- 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 adbe421835c1..7efd7072cca5 100644
--- 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);
--
2.20.1
