On Wed, Sep 27, 2023 at 05:52:14AM +0000, Justin Stitt wrote: > `strncpy` is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > A suitable replacement is `strscpy` [2] due to the fact that it > guarantees NUL-termination on the destination buffer without > unnecessarily NUL-padding.
This is weird -- I think hmc_id needs to be marked __nonstring, and the commit log should talk about how it appears to be not %NUL terminated. The bounce buffer is weird -- it seems like hmc_id could be made a regular C string by being changed to MHC_ID_LEN + 1, and then everything would work correctly without needing a bounce buffer, etc. (Well, it would need explicit %NUL termination after the copy_from_user()). But if that refactor doesn't sound right to maintainers, then I'd agree that this patch is fine (though capturing the __nonstring bit might be nice): Reviewed-by: Kees Cook <[email protected]> -Kees > > Link: > https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings > [1] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html > [2] > Link: https://github.com/KSPP/linux/issues/90 > Cc: [email protected] > Signed-off-by: Justin Stitt <[email protected]> > --- > Note: build-tested only. > --- > drivers/misc/ibmvmc.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/misc/ibmvmc.c b/drivers/misc/ibmvmc.c > index 2101eb12bcba..6d9ed9325f9f 100644 > --- a/drivers/misc/ibmvmc.c > +++ b/drivers/misc/ibmvmc.c > @@ -1249,9 +1249,7 @@ static long ibmvmc_ioctl_sethmcid(struct > ibmvmc_file_session *session, > return -EIO; > } > > - /* Make sure buffer is NULL terminated before trying to print it */ > - memset(print_buffer, 0, HMC_ID_LEN + 1); > - strncpy(print_buffer, hmc->hmc_id, HMC_ID_LEN); > + strscpy(print_buffer, hmc->hmc_id, sizeof(print_buffer)); > pr_info("ibmvmc: sethmcid: Set HMC ID: \"%s\"\n", print_buffer); > > memcpy(buffer->real_addr_local, hmc->hmc_id, HMC_ID_LEN); > > --- > base-commit: 6465e260f48790807eef06b583b38ca9789b6072 > change-id: 20230927-strncpy-drivers-misc-ibmvmc-c-534349716fa4 > > Best regards, > -- > Justin Stitt <[email protected]> > -- Kees Cook
