From 4fe54f509304ea6cc80a40620cac860c57edf7f3 Mon Sep 17 00:00:00 2001 From: Vit Kabele Date: Thu, 27 Oct 2022 19:50:06 +0200 Subject: [PATCH] ACPICA: Check that EBDA pointer is in valid memory ACPICA commit cc9e7763ceb2e2649fe3422130416d84a3c6854a If the memory at 0x40e is uninitialized, the retrieved physical_memory address of EBDA may be beyond the low memory (i.e. above 640K). If so, the kernel may unintentionally access the VGA memory, that might not be decoded or even present in case of virtualization. Link: https://github.com/acpica/acpica/commit/cc9e7763 Signed-off-by: Vit Kabele Signed-off-by: Bob Moore Signed-off-by: Rafael J. Wysocki --- drivers/acpi/acpica/tbxfroot.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/acpi/acpica/tbxfroot.c b/drivers/acpi/acpica/tbxfroot.c index 3d09e3f6bd43..ede2745838c8 100644 --- a/drivers/acpi/acpica/tbxfroot.c +++ b/drivers/acpi/acpica/tbxfroot.c @@ -139,7 +139,11 @@ acpi_find_root_pointer(acpi_physical_address *table_address) /* EBDA present? */ - if (physical_address > 0x400) { + /* + * Check that the EBDA pointer from memory is sane and does not point + * above valid low memory + */ + if (physical_address > 0x400 && physical_address < 0xA0000) { /* * 1b) Search EBDA paragraphs (EBDA is required to be a * minimum of 1K length)