efi: Fix handling of multiple efi_fake_mem= entries (484a418d) · Commits · 戴 / test

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 "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 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

drivers/firmware/efi/fake_mem.c

+16 −15

Original line number	Diff line number	Diff line
		@@ -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();

drivers/firmware/efi/memmap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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())

include/linux/efi.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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);

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