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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Darren Kenny <darren.kenny@oracle.com>
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Date: Fri, 11 Dec 2020 15:03:13 +0000
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Subject: [PATCH] kern/efi/mm: Fix possible NULL pointer dereference
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The model of grub_efi_get_memory_map() is that if memory_map is NULL,
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then the purpose is to discover how much memory should be allocated to
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it for the subsequent call.
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The problem here is that with grub_efi_is_finished set to 1, there is no
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check at all that the function is being called with a non-NULL memory_map.
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While this MAY be true, we shouldn't assume it.
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The solution to this is to behave as expected, and if memory_map is NULL,
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then don't try to use it and allow memory_map_size to be filled in, and
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return 0 as is done later in the code if the buffer is too small (or NULL).
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Additionally, drop unneeded ret = 1.
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Fixes: CID 96632
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Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/kern/efi/mm.c | 23 ++++++++++++++++-------
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1 file changed, 16 insertions(+), 7 deletions(-)
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diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
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index 306924f73..2d9c9032b 100644
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--- a/grub-core/kern/efi/mm.c
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+++ b/grub-core/kern/efi/mm.c
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@@ -372,16 +372,25 @@ grub_efi_get_memory_map (grub_efi_uintn_t *memory_map_size,
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if (grub_efi_is_finished)
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{
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int ret = 1;
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- if (*memory_map_size < finish_mmap_size)
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+
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+ if (memory_map != NULL)
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{
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- grub_memcpy (memory_map, finish_mmap_buf, *memory_map_size);
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+ if (*memory_map_size < finish_mmap_size)
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+ {
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+ grub_memcpy (memory_map, finish_mmap_buf, *memory_map_size);
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+ ret = 0;
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+ }
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+ else
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+ grub_memcpy (memory_map, finish_mmap_buf, finish_mmap_size);
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+ }
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+ else
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+ {
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+ /*
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+ * Incomplete, no buffer to copy into, same as
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+ * GRUB_EFI_BUFFER_TOO_SMALL below.
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+ */
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ret = 0;
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}
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- else
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- {
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- grub_memcpy (memory_map, finish_mmap_buf, finish_mmap_size);
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- ret = 1;
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- }
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*memory_map_size = finish_mmap_size;
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if (map_key)
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*map_key = finish_key;
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