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

    On Thu, Mar 28, 2024 at 03:04:50PM +0100, Arnd Bergmann wrote:
    > 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.
    >
    I also tried cleaning these up but Kees informed me that this subsystem
    is maintained elsewhere:

    https://lore.kernel.org/all/202308241612.DFE4119@keescook/

    I am not sure if you can get changes through by the traditional means.

    >
    > 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
    >
    Thanks
    Justin

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