From 2c43798717ee5af0b666fc49b7b8c1d992563f06 Mon Sep 17 00:00:00 2001
From: nilusyi <nilusyi@tencent.com>
Date: Thu, 26 Dec 2024 19:24:32 +0800
Subject: [PATCH 4/4] kern/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>
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
Tested-by: Renata Ravanelli <rravanel@redhat.com>
---
 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 48ded4e2e..8ff0835d5 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;
-- 
2.41.1