linux-kernel - [PATCH v2 3/4] efi: Fix efi_memmap

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Date:   Tue, 31 Dec 2019 14:04:33 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     mingo@...hat.com
Cc:     Taku Izumi <izumi.taku@...fujitsu.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        kexec@...ts.infradead.org, x86@...nel.org
Subject: [PATCH v2 3/4] efi: Fix efi_memmap_alloc() leaks

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.

Cc: Taku Izumi <izumi.taku@...fujitsu.com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 drivers/firmware/efi/memmap.c |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
index 2b81ee6858a9..188ab3cd5c52 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 (WARN_ON(slab_is_available() && (flags & EFI_MEMMAP_MEMBLOCK)))
+		return;
+
+	if (flags & EFI_MEMMAP_MEMBLOCK) {
+		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.
@@ -209,6 +231,8 @@ int __init efi_memmap_install(phys_addr_t addr, unsigned int nr_map,
 	data.desc_size = efi.memmap.desc_size;
 	flags |= efi.memmap.flags & EFI_MEMMAP_LATE;
 
+	efi_memmap_free();
+
 	return __efi_memmap_init(&data, flags);
 }