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, so I'm not sure what's going on. Changing it to strspy() avoids the warning. In this case the existing check for zero-termination would fail but can be replaced with an error check.
Signed-off-by: Arnd Bergmann arnd@arndb.de --- This is from randconfig testing with random gcc versions, a .config to reproduce is at https://pastebin.com/r13yezkU --- drivers/staging/greybus/fw-management.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/greybus/fw-management.c b/drivers/staging/greybus/fw-management.c index 3054f084d777..35bfdd5f32d2 100644 --- a/drivers/staging/greybus/fw-management.c +++ b/drivers/staging/greybus/fw-management.c @@ -303,13 +303,13 @@ 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(request.firmware_tag, tag, GB_FIRMWARE_TAG_MAX_SIZE);
/* * 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; }