linux-kernel - [PATCH v1] ACPICA: Switch back to using strncpy() in acpi_ut_safe

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Message-ID: <12685690.O9o76ZdvQC@rjwysocki.net>
Date: Thu, 29 May 2025 17:43:13 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux ACPI <linux-acpi@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Saket Dumbre <saket.dumbre@...el.com>, Ahmed Salem <x0rw3ll@...il.com>,
 Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
Subject:
 [PATCH v1] ACPICA: Switch back to using strncpy() in acpi_ut_safe_strncpy()

From: Ahmed Salem <x0rw3ll@...il.com>

ACPICA commit b90d0d65ec97ff8279ad826f4102e0d31c5f662a

I mistakenly replaced strncpy() with memcpy() in commit ebf27765421c
("ACPICA: Replace strncpy() with memcpy()"), not realizing the entire
context behind *why* strncpy() was used.

In this safer implementation of strncpy(), it does not make
sense to use memcpy() only to null-terminate strings passed to
acpi_ut_safe_strncpy() one byte early.

The consequences of doing so are understandably *bad*, as was
evident by the kernel test bot reporting problems [1].

Fixes: ebf27765421c ("ACPICA: Replace strncpy() with memcpy()")
Link: https://lore.kernel.org/all/202505081033.50e45ff4-lkp@intel.com [1]
Reported-by: kernel test robot <oliver.sang@...el.com>
Closes: https://lore.kernel.org/oe-lkp/202505081033.50e45ff4-lkp@intel.com
Link: https://github.com/acpica/acpica/commit/b90d0d65
Signed-off-by: Ahmed Salem <x0rw3ll@...il.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 utnonansi.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -Nurp linux.before_name/drivers/acpi/acpica/utnonansi.c linux.after_name/drivers/acpi/acpica/utnonansi.c
--- linux.before_name/drivers/acpi/acpica/utnonansi.c	2025-05-29 17:24:27.130073452 +0200
+++ linux.after_name/drivers/acpi/acpica/utnonansi.c	2025-05-29 17:24:22.076757944 +0200
@@ -168,7 +168,7 @@ void acpi_ut_safe_strncpy(char *dest, ch
 {
 	/* Always terminate destination string */

-	memcpy(dest, source, dest_size);
+	strncpy(dest, source, dest_size);
 	dest[dest_size - 1] = 0;
 }