On Thu, Mar 28, 2024, at 16:00, Dan Carpenter wrote: > On Thu, Mar 28, 2024 at 03:04:54PM +0100, Arnd Bergmann wrote: >> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> >> --- >> 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); > > This needs to be strscpy_pad() or it risks an information leak. Right, I think I misread the code thinking that the strncpy() destination was user provided, but I see now that this copy is from user-provided data into the stack, so the padding is indeed stale stack data. I could not find out whether this gets copied back to userspace, but adding the padding is safer indeed. >> >> /* >> * The firmware-tag should be NULL terminated, otherwise throw error and > ^^^^^^^^^^^^^^^^ > These comments are out of date. > >> * 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"); > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > More out of date prints. I had thought about changing it when I did the patch, but could not come up with anything that describes the error condition better: the cause of the -E2BIG error is still the missing NUL-termination in the provided string. Maybe we should instead not print a warning at all? The general rule is that user triggered operations should not lead to spamming the kernel logs. Arnd
