linux-kernel - [PATCH 27/32] ACPICA: acpi_dmar_andd: Replace 1-element array with flexible array

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Date:   Wed, 05 Apr 2023 15:55:13 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Bob Moore <robert.moore@...el.com>,
        Kees Cook <kees@...flux.net>
Subject: [PATCH 27/32] ACPICA: acpi_dmar_andd: Replace 1-element array with flexible array

From: Kees Cook <kees@...flux.net>

ACPICA commit 3c19ae70424e9ab1e1b805203d300d2660f9a2f7

Similar to "Replace one-element array with flexible-array", replace the
1-element array with a proper flexible array member as defined by C99.

This allows the code to operate without tripping compile-time and run-
time bounds checkers (e.g. via __builtin_object_size(), -fsanitize=bounds,
and/or -fstrict-flex-arrays=3).

The handling of struct acpi_dmar_andd by acpi_dm_dump_dmar() appears to
expect a single trailing char for calculating table offsets. Keep a char
in the union to avoid any code changes appearing in the .text or .data
sections.

Link: https://github.com/acpica/acpica/commit/3c19ae70
Signed-off-by: Kees Cook <kees@...flux.net>
Signed-off-by: Bob Moore <robert.moore@...el.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 include/acpi/actbl1.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/acpi/actbl1.h b/include/acpi/actbl1.h
index 6ee7437537db..58b0490a2ad1 100644
--- a/include/acpi/actbl1.h
+++ b/include/acpi/actbl1.h
@@ -901,7 +901,10 @@ struct acpi_dmar_andd {
 	struct acpi_dmar_header header;
 	u8 reserved[3];
 	u8 device_number;
-	char device_name[1];
+	union {
+		char __pad;
+		 ACPI_FLEX_ARRAY(char, device_name);
+	};
 };

 /* 5: SOC Integrated Address Translation Cache Reporting Structure */
-- 
2.35.3