Messages in this thread | | | Date | Thu, 14 Sep 2023 22:40:37 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH] hwmon: (ibmpowernv) refactor deprecated strncpy |
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On 9/14/23 22:24, Kees Cook wrote: > On Thu, Sep 14, 2023 at 11:21:06PM +0000, Justin Stitt wrote: >> `strncpy` is deprecated for use on NUL-terminated destination strings [1]. >> >> 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 since `buf` is already zero-initialized. >> >> 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> >> --- >> drivers/hwmon/ibmpowernv.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/hwmon/ibmpowernv.c b/drivers/hwmon/ibmpowernv.c >> index 594254d6a72d..57d829dbcda6 100644 >> --- a/drivers/hwmon/ibmpowernv.c >> +++ b/drivers/hwmon/ibmpowernv.c >> @@ -234,7 +234,7 @@ static int get_sensor_index_attr(const char *name, u32 *index, char *attr) >> if (copy_len >= sizeof(buf)) >> return -EINVAL; >> >> - strncpy(buf, hash_pos + 1, copy_len); >> + strscpy(buf, hash_pos + 1, copy_len); > > This is another case of precise byte copying -- this just needs to be > memcpy. Otherwise this truncates the trailing character. Imagine a name > input of "fan#2-data". "buf" wants to get "2". copy_len is 1, and > strscpy would eat it. :) >
It is really sad that the submitters of such "cleanup" patches can't be bothered to check what they are doing. They can't even be bothered to write a coccinelle script that would avoid pitfalls like this one, and they expect others to do their homework for them.
And then people wonder why there is maintainer burnout. I am so tired of that.
Guenter
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