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From 1c38760731eefdbd5e9ce288009d6d19afcff004 Mon Sep 17 00:00:00 2001
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From: Peter Jones <pjones@redhat.com>
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Date: Wed, 7 Dec 2016 16:34:20 -0500
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Subject: [PATCH 4/4] efi: efi_memmap_insert(): don't split regions with
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invalid sizes.
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Some machines, such as the Lenovo ThinkPad W541 with firmware GNET80WW
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(2.28), include memory map entries with phys_addr=0x0 and num_pages=0.
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If we're inserting a new memmap and we find a map that is either 0
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pages or all of possible memory (or more!), skip it. When a map exists
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at 0 that's 0 pages, the "end" math here winds up making *every* address
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within the range, and so it'll try to split that entry, and things go
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poorly after that. The same would be true if num_pages were (u64)-1LL
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(all bits set) or (u64)-1LL >> EFI_PAGE_SHIFT (i.e. all bits set as a
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size in bytes, but then shifted to page size to fill the table in).
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Don't even try to split those entries, they're nonsense.
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Signed-off-by: Peter Jones <pjones@redhat.com>
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---
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drivers/firmware/efi/memmap.c | 7 +++++++
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1 file changed, 7 insertions(+)
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diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
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index 5b71c717..f8c6870 100644
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--- a/drivers/firmware/efi/memmap.c
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+++ b/drivers/firmware/efi/memmap.c
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@@ -244,6 +244,13 @@ void __init efi_memmap_insert(struct efi_memory_map *old_memmap, void *buf,
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/* copy original EFI memory descriptor */
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memcpy(new, old, old_memmap->desc_size);
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md = new;
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+ if (md->num_pages == 0 ||
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+ md->num_pages >= (((u64)-1LL) >> EFI_PAGE_SHIFT)) {
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+ pr_warn("%s: Skipping absurd memory map entry for 0x%llx pages at 0x%016llx.\n",
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+ __func__, md->num_pages, md->phys_addr);
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+ continue;
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+ }
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+
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start = md->phys_addr;
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end = md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT) - 1;
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--
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2.9.3
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