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Subject[PATCH 12/13] efi: Fix efi_memmap_alloc() leaks
Date
From: Dan Williams <dan.j.williams@intel.com>

With efi_fake_memmap() and efi_arch_mem_reserve() the efi table may be
updated and replaced multiple times. When that happens a previous
dynamically allocated efi memory map can be garbage collected. Use the
new EFI_MEMMAP_{SLAB,MEMBLOCK} flags to detect when a dynamically
allocated memory map is being replaced.

Debug statements in efi_memmap_free() reveal:

efi: __efi_memmap_free:37: phys: 0x23ffdd580 size: 2688 flags: 0x2
efi: __efi_memmap_free:37: phys: 0x9db00 size: 2640 flags: 0x2
efi: __efi_memmap_free:37: phys: 0x9e580 size: 2640 flags: 0x2

...a savings of 7968 bytes on a qemu boot with 2 entries specified to
efi_fake_mem=.

[ ardb: added a comment to clarify that efi_memmap_free() does nothing when
called from efi_clean_memmap(), i.e., with data->flags == 0x0 ]

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/firmware/efi/memmap.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
index 04dfa56b994b..501672166502 100644
--- a/drivers/firmware/efi/memmap.c
+++ b/drivers/firmware/efi/memmap.c
@@ -29,6 +29,28 @@ 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)
+{
+ if (flags & EFI_MEMMAP_MEMBLOCK) {
+ if (slab_is_available())
+ memblock_free_late(phys, size);
+ else
+ memblock_free(phys, size);
+ } else if (flags & EFI_MEMMAP_SLAB) {
+ struct page *p = pfn_to_page(PHYS_PFN(phys));
+ unsigned int order = get_order(size);
+
+ free_pages((unsigned long) page_address(p), order);
+ }
+}
+
+static void __init efi_memmap_free(void)
+{
+ __efi_memmap_free(efi.memmap.phys_map,
+ efi.memmap.desc_size * efi.memmap.nr_map,
+ efi.memmap.flags);
+}
+
/**
* efi_memmap_alloc - Allocate memory for the EFI memory map
* @num_entries: Number of entries in the allocated map.
@@ -100,6 +122,9 @@ static int __init __efi_memmap_init(struct efi_memory_map_data *data)
return -ENOMEM;
}

+ /* NOP if data->flags & (EFI_MEMMAP_MEMBLOCK | EFI_MEMMAP_SLAB) == 0 */
+ efi_memmap_free();
+
map.phys_map = data->phys_map;
map.nr_map = data->size / data->desc_size;
map.map_end = map.map + data->size;
--
2.20.1
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