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Thu, 27 Jul 2023 15:09:34 -0700 (PDT) Date: Thu, 27 Jul 2023 22:09:29 +0000 Mime-Version: 1.0 X-B4-Tracking: v=1; b=H4sIABjrwmQC/x3MQQqEMAxG4atI1gZ+6zCiVxEXrY1jNlUaFEG8u 2WW3+K9m0yyitFQ3ZTlVNMtFTR1RfPq009YYzE5uBad69i2I0U+LHCYowPAHyC0+ML3S0+l27M sev2f4/Q8L8MihdBjAAAA X-Developer-Key: i=justinstitt@google.com; a=ed25519; pk=tC3hNkJQTpNX/gLKxTNQKDmiQl6QjBNCGKJINqAdJsE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1690495773; l=2722; i=justinstitt@google.com; s=20230717; h=from:subject:message-id; bh=oD0r9GQJcI4a0oPPFKD+f4eCazsB8WXRECfFQ/3Qn80=; b=RMEEkMB9gj5yDuIGuIqJVfiAW714ytVo21T7+/g2zrDgaM+Trm12x329hvrQ6qpkXQkBKdNp7 h1YTuOzeph4DYE6Y7PJqPk4FGt00qNiQKla88lXSQoet8fLsPbVG5Uu X-Mailer: b4 0.12.3 Message-ID: <20230727-sound-usb-bcd2000-v1-1-0dc73684b2f0@google.com> Subject: [PATCH] ALSA: bcd2000: refactor deprecated strncpy From: Justin Stitt To: Jaroslav Kysela , Takashi Iwai Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Justin Stitt Message-ID-Hash: JPNJW45AVVDIABF3ZBWFCFFA3NYHBH7U X-Message-ID-Hash: JPNJW45AVVDIABF3ZBWFCFFA3NYHBH7U X-MailFrom: 3HuvCZAsKCi0SdbcRWbcRccPXXPUN.LXVJUbJ-MNeNUJUbJ-YaXSNLc.XaP@flex--justinstitt.bounces.google.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: `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_ always the case for `strncpy`! It should be noted that, in this case, the destination buffer has a length strictly greater than the source string. Moreover, the source string is NUL-terminated (and so is the destination) which means there was no real bug happening here. Nonetheless, this patch would get us one step closer to eliminating the `strncpy` API in the kernel, as its use is too ambiguous. We need to favor less ambiguous replacements such as: strscpy, strscpy_pad, strtomem and strtomem_pad (amongst others). Technically, my patch yields subtly different behavior. The original implementation with `strncpy` would fill the entire destination buffer with null bytes [3] while `strscpy` will leave the junk, uninitialized bytes trailing after the _mandatory_ NUL-termination. So, if somehow `card->driver` or `card->shortname` require this NUL-padding behavior then `strscpy_pad` should be used. My interpretation, though, is that the aforementioned fields are just fine as NUL-terminated strings. Please correct my assumptions if needed and I'll send in a v2. [1]: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [2]: manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [3]: https://linux.die.net/man/3/strncpy Link: https://github.com/KSPP/linux/issues/90 Link: https://lore.kernel.org/r/20230727-sound-xen-v1-1-89dd161351f1@google.com (related ALSA patch) Signed-off-by: Justin Stitt --- sound/usb/bcd2000/bcd2000.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- base-commit: 57012c57536f8814dec92e74197ee96c3498d24e change-id: 20230727-sound-usb-bcd2000-400b3060a9f9 Best regards, -- Justin Stitt diff --git a/sound/usb/bcd2000/bcd2000.c b/sound/usb/bcd2000/bcd2000.c index 7aec0a95c609..392b4d8e9e76 100644 --- a/sound/usb/bcd2000/bcd2000.c +++ b/sound/usb/bcd2000/bcd2000.c @@ -395,8 +395,8 @@ static int bcd2000_probe(struct usb_interface *interface, snd_card_set_dev(card, &interface->dev); - strncpy(card->driver, "snd-bcd2000", sizeof(card->driver)); - strncpy(card->shortname, "BCD2000", sizeof(card->shortname)); + strscpy(card->driver, "snd-bcd2000", sizeof(card->driver)); + strscpy(card->shortname, "BCD2000", sizeof(card->shortname)); usb_make_path(bcd2k->dev, usb_path, sizeof(usb_path)); snprintf(bcd2k->card->longname, sizeof(bcd2k->card->longname), "Behringer BCD2000 at %s",