Hi,

On Mon, Apr 08, 2024 at 09:48:11PM +0200, Arnd Bergmann wrote:

From: Arnd Bergmann arnd@arndb.de

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@arndb.de

This patch helps out with [1].

Reviewed-by: Justin Stitt justinstitt@google.com

---

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