Re: [PATCH] hwmon: (ibmpowernv) refactor deprecated strncpy
From: Kees Cook <hidden>
Date: 2023-09-15 05:24:57
Also in:
linux-hardening, linux-hwmon, lkml
On Thu, Sep 14, 2023 at 11:21:06PM +0000, Justin Stitt wrote:
quoted hunk ↗ jump to hunk
`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. :) -Kees
err = kstrtou32(buf, 10, index); if (err) --- base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec change-id: 20230914-strncpy-drivers-hwmon-ibmpowernv-c-80a03f16d93a Best regards, -- Justin Stitt [off-list ref]
-- Kees Cook