From bdf5c1b3607bd6384ac5319caad2d8107130ace1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Stefan=20Br=C3=BCns?= Date: Sun, 9 Oct 2016 22:17:07 +0200 Subject: efi_loader: Fix memory map size check to avoid out-of-bounds access MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Alexander Graf Signed-off-by: Alexander Graf --- lib/efi_loader/efi_memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c index ebe8e94c83..1d23783020 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 */ -- cgit v1.2.3