[PATCH 06/11] acpi: avoid warning for truncated string copy

Arnd Bergmann
2024-03-28T14:06:42Z

From: Arnd Bergmann <arnd@arndb.de>

gcc -Wstringop-truncation warns about copying a string that results in a
missing nul termination:

drivers/acpi/acpica/tbfind.c: In function 'acpi_tb_find_table':
drivers/acpi/acpica/tbfind.c:60:9: error: 'strncpy' specified bound 6 equals destination size [-Werror=stringop-truncation]
60 | strncpy(header.oem_id, oem_id, ACPI_OEM_ID_SIZE);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/acpi/acpica/tbfind.c:61:9: error: 'strncpy' specified bound 8 equals destination size [-Werror=stringop-truncation]
61 | strncpy(header.oem_table_id, oem_table_id, ACPI_OEM_TABLE_ID_SIZE);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This one is intentional, so rewrite the code in a way that avoids the
warning. Since there is already an extra strlen() and an overflow check,
the actual size to be copied is already known here.

Fixes: 47c08729bf1c ("ACPICA: Fix for LoadTable operator, input strings")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/acpi/acpica/tbfind.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/acpi/acpica/tbfind.c b/drivers/acpi/acpica/tbfind.c
index 1c1b2e284bd9..472ce2a6624b 100644
--- a/drivers/acpi/acpica/tbfind.c
+++ b/drivers/acpi/acpica/tbfind.c
@@ -36,7 +36,7 @@ acpi_tb_find_table(char *signature,
{
acpi_status status = AE_OK;
struct acpi_table_header header;
- u32 i;
+ u32 len, i;

ACPI_FUNCTION_TRACE(tb_find_table);

@@ -46,19 +46,18 @@ acpi_tb_find_table(char *signature,
return_ACPI_STATUS(AE_BAD_SIGNATURE);
}

- /* Don't allow the OEM strings to be too long */
-
- if ((strlen(oem_id) > ACPI_OEM_ID_SIZE) ||
- (strlen(oem_table_id) > ACPI_OEM_TABLE_ID_SIZE)) {
- return_ACPI_STATUS(AE_AML_STRING_LIMIT);
- }
-
/* Normalize the input strings */

memset(&header, 0, sizeof(struct acpi_table_header));
ACPI_COPY_NAMESEG(header.signature, signature);
- strncpy(header.oem_id, oem_id, ACPI_OEM_ID_SIZE);
- strncpy(header.oem_table_id, oem_table_id, ACPI_OEM_TABLE_ID_SIZE);
+ len = strlen(oem_id);
+ if (len > ACPI_OEM_ID_SIZE)
+ return_ACPI_STATUS(AE_AML_STRING_LIMIT);
+ memcpy(header.oem_id, oem_id, len);
+ len = strlen(oem_table_id);
+ if (len > ACPI_OEM_TABLE_ID_SIZE)
+ return_ACPI_STATUS(AE_AML_STRING_LIMIT);
+ memcpy(header.oem_table_id, oem_table_id, len);

/* Search for the table */

--
2.39.2