Messages in this thread Patch in this message | | | Date | Mon, 2 Oct 2023 11:01:02 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] ibmvmc: replace deprecated strncpy with strscpy |
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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 <keescook@chromium.org>
-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: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> > --- > 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 <justinstitt@google.com> >
-- Kees Cook
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