File 0017-efi_loader-Fix-memory-map-size-chec.patch of Package u-boot-a20-olinuxino-lime

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File 0017-efi_loader-Fix-memory-map-size-chec.patch of Package u-boot-a20-olinuxino-lime

From d8c0aafcdfb413eb414801c58c23a528f4e0a8b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Br=C3=BCns?= <stefan.bruens@rwth-aachen.de>
Date: Sun, 9 Oct 2016 22:17:07 +0200
Subject: [PATCH] efi_loader: Fix memory map size check to avoid out-of-bounds
 access
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The current efi_get_memory_map() function overwrites the map_size
property before reading its value. That way the sanity check whether our
memory map fits into the given array always succeeds, potentially
overwriting arbitrary payload memory.

This patch moves the property update write after its sanity check, so
that the check actually verifies the correct value.

So far this has not triggered any known bugs, but we're better off safe
than sorry.

If the buffer is to small, the returned memory_map_size indicates the
required size to the caller.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
 lib/efi_loader/efi_memory.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
index ebe8e94..1d23783 100644
--- a/lib/efi_loader/efi_memory.c
+++ b/lib/efi_loader/efi_memory.c
@@ -336,6 +336,7 @@ efi_status_t efi_get_memory_map(unsigned long *memory_map_size,
 	ulong map_size = 0;
 	int map_entries = 0;
 	struct list_head *lhandle;
+	unsigned long provided_map_size = *memory_map_size;
 
 	list_for_each(lhandle, &efi_mem)
 		map_entries++;
@@ -350,7 +351,7 @@ efi_status_t efi_get_memory_map(unsigned long *memory_map_size,
 	if (descriptor_version)
 		*descriptor_version = EFI_MEMORY_DESCRIPTOR_VERSION;
 
-	if (*memory_map_size < map_size)
+	if (provided_map_size < map_size)
 		return EFI_BUFFER_TOO_SMALL;
 
 	/* Copy list into array */

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File 0017-efi_loader-Fix-memory-map-size-chec.patch of Package u-boot-a20-olinuxino-lime

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