Hi,
On Mon, Apr 08, 2024 at 09:48:11PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> gcc-10 warns about a strncpy() that does not enforce zero-termination:
>
> In file included from include/linux/string.h:369,
> from drivers/staging/greybus/fw-management.c:9:
> In function 'strncpy',
> inlined from 'fw_mgmt_backend_fw_update_operation' at drivers/staging/greybus/fw-management.c:306:2:
> include/linux/fortify-string.h:108:30: error: '__builtin_strncpy' specified bound 10 equals destination size [-Werror=stringop-truncation]
> 108 | #define __underlying_strncpy __builtin_strncpy
> | ^
> include/linux/fortify-string.h:187:9: note: in expansion of macro '__underlying_strncpy'
> 187 | return __underlying_strncpy(p, q, size);
> | ^~~~~~~~~~~~~~~~~~~~
>
> For some reason, I cannot reproduce this with gcc-9 or gcc-11, and I only
> get a warning for one of the four related strncpy()s, so I'm not
> sure what's going on.
>
> Change all four to strscpy_pad(), which is the safest replacement here,
> as it avoids ending up with uninitialized stack data in the tag name.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
This patch helps out with [1].
Reviewed-by: Justin Stitt <justinstitt@xxxxxxxxxx>
> ---
> v2
> - use strscpy_pad()
> - use two-argument form
> - change all four instances, not just the one that produced the warning
> ---
> drivers/staging/greybus/fw-management.c | 12 +++++-------
> 1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/staging/greybus/fw-management.c b/drivers/staging/greybus/fw-management.c
> index 3054f084d777..a47385175582 100644
> --- a/drivers/staging/greybus/fw-management.c
> +++ b/drivers/staging/greybus/fw-management.c
> @@ -123,8 +123,7 @@ static int fw_mgmt_interface_fw_version_operation(struct fw_mgmt *fw_mgmt,
> fw_info->major = le16_to_cpu(response.major);
> fw_info->minor = le16_to_cpu(response.minor);
>
> - strncpy(fw_info->firmware_tag, response.firmware_tag,
> - GB_FIRMWARE_TAG_MAX_SIZE);
> + strscpy_pad(fw_info->firmware_tag, response.firmware_tag);
>
> /*
> * The firmware-tag should be NULL terminated, otherwise throw error but
> @@ -153,7 +152,7 @@ static int fw_mgmt_load_and_validate_operation(struct fw_mgmt *fw_mgmt,
> }
>
> request.load_method = load_method;
> - strncpy(request.firmware_tag, tag, GB_FIRMWARE_TAG_MAX_SIZE);
> + strscpy_pad(request.firmware_tag, tag);
>
> /*
> * The firmware-tag should be NULL terminated, otherwise throw error and
> @@ -249,8 +248,7 @@ static int fw_mgmt_backend_fw_version_operation(struct fw_mgmt *fw_mgmt,
> struct gb_fw_mgmt_backend_fw_version_response response;
> int ret;
>
> - strncpy(request.firmware_tag, fw_info->firmware_tag,
> - GB_FIRMWARE_TAG_MAX_SIZE);
> + strscpy_pad(request.firmware_tag, fw_info->firmware_tag);
>
> /*
> * The firmware-tag should be NULL terminated, otherwise throw error and
> @@ -303,13 +301,13 @@ static int fw_mgmt_backend_fw_update_operation(struct fw_mgmt *fw_mgmt,
> struct gb_fw_mgmt_backend_fw_update_request request;
> int ret;
>
> - strncpy(request.firmware_tag, tag, GB_FIRMWARE_TAG_MAX_SIZE);
> + ret = strscpy_pad(request.firmware_tag, tag);
>
> /*
> * The firmware-tag should be NULL terminated, otherwise throw error and
> * fail.
> */
> - if (request.firmware_tag[GB_FIRMWARE_TAG_MAX_SIZE - 1] != '\0') {
> + if (ret == -E2BIG) {
> dev_err(fw_mgmt->parent, "backend-update: firmware-tag is not NULL terminated\n");
> return -EINVAL;
> }
> --
> 2.39.2
>
>
Link: https://github.com/KSPP/linux/issues/90 [1]
Thanks
Justin
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