From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 16 Oct 2024 16:20:24 +1100
Subject: [PATCH] acpi: Fix out of bounds access in grub_acpi_xsdt_find_table()

The calculation of the size of the table was incorrect (copy/pasta from
grub_acpi_rsdt_find_table() I assume...). The entries are 64-bit long.

This causes us to access beyond the end of the table which is causing
crashes during boot on some systems. Typically this is causing a crash
on VMWare when using UEFI and enabling serial autodetection, as

grub_acpi_find_table (GRUB_ACPI_SPCR_SIGNATURE);

Will goes past the end of the table (the SPCR table doesn't exits)

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 grub-core/kern/acpi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grub-core/kern/acpi.c b/grub-core/kern/acpi.c
index 48ded4e2ea6e..8ff0835d501f 100644
--- a/grub-core/kern/acpi.c
+++ b/grub-core/kern/acpi.c
@@ -75,7 +75,7 @@ grub_acpi_xsdt_find_table (struct grub_acpi_table_header *xsdt, const char *sig)
     return 0;
 
   ptr = (grub_unaligned_uint64_t *) (xsdt + 1);
-  s = (xsdt->length - sizeof (*xsdt)) / sizeof (grub_uint32_t);
+  s = (xsdt->length - sizeof (*xsdt)) / sizeof (grub_uint64_t);
   for (; s; s--, ptr++)
     {
       struct grub_acpi_table_header *tbl;