On Wed, Jul 26, 2023 at 09:12:18PM +0000, justinstitt@google.com wrote:
`strncpy` is deprecated for use on NUL-terminated destination strings [1].
A suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on its destination buffer argument which is _not_ the case for `strncpy`!
It was pretty difficult, in this case, to try and figure out whether or not the destination buffer was zero-initialized. If it is and this behavior is relied on then perhaps `strscpy_pad` is the preferred option here.
Kees was able to help me out and identify the following code snippet which seems to show that the destination buffer is zero-initialized.
| skl = devm_kzalloc(&pci->dev, sizeof(*skl), GFP_KERNEL);
With this information, I opted for `strscpy` since padding is seemingly not required.
We did notice that str_elem->string is 44 bytes, but skl->lib_info[ref_count].name is 128 bytes. If str_elem->string isn't NUL-terminated, this can still hit an over-read condition (though CONFIG_FORTIFY_SOURCE would have caught it both before with strncpy() and now with strscpy()). So I assume it is expected to be NUL-terminated?
Also within this patch is a change to an instance of `x > y - 1` to `x >= y` which tends to be more robust and readable. Consider, for instance, if `y` was somehow `INT_MIN`.
I'd split this change into a separate patch -- it's logically unrelated (but seems a reasonable cleanup).
Link: https://github.com/KSPP/linux/issues/90 Suggested-by: Kees Cook keescook@chromium.org Signed-off-by: Justin Stitt justinstitt@google.com
sound/soc/intel/skylake/skl-topology.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/sound/soc/intel/skylake/skl-topology.c b/sound/soc/intel/skylake/skl-topology.c index 96cfebded072..67f08ec3a2ea 100644 --- a/sound/soc/intel/skylake/skl-topology.c +++ b/sound/soc/intel/skylake/skl-topology.c @@ -3154,12 +3154,12 @@ static int skl_tplg_fill_str_mfest_tkn(struct device *dev,
switch (str_elem->token) { case SKL_TKN_STR_LIB_NAME:
if (ref_count > skl->lib_count - 1) {
if (ref_count >= skl->lib_count) { ref_count = 0; return -EINVAL;
strncpy(skl->lib_info[ref_count].name,
strscpy(skl->lib_info[ref_count].name, str_elem->string, ARRAY_SIZE(skl->lib_info[ref_count].name));
base-commit: 0b4a9fdc9317440a71d4d4c264a5650bf4a90f3c change-id: 20230726-asoc-intel-skylake-remove-deprecated-strncpy-9dbcfc26040c
Best regards,
Justin Stitt justinstitt@google.com