From 30bed99e0c6335b711119b9fda806da7b4031dfb Mon Sep 17 00:00:00 2001 From: Justin Stitt Date: Mon, 7 Aug 2023 18:22:30 +0000 Subject: [PATCH] um: vector: refactor deprecated strncpy `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`! In this case, we are able to drop the now superfluous `... - 1` instances because `strscpy` will automatically truncate the last byte by setting it to a NUL byte if the source size exceeds the destination size or if the source string is not NUL-terminated. I've also opted to remove the seemingly useless char* casts. I'm not sure why they're present at all since (after expanding the `ifr_name` macro) `ifr.ifr_ifrn.ifrn_name` is a char* already. All in all, `strscpy` is a more robust and less ambiguous interface while also letting us remove some `... -1`'s which cleans things up a bit. [1]: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [2]: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt Acked-by: Anton Ivanov Link: https://lore.kernel.org/r/20230807-arch-um-drivers-v1-1-10d602c5577a@google.com Signed-off-by: Kees Cook --- arch/um/drivers/vector_user.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c index c650e428432b..c719e1ec4645 100644 --- a/arch/um/drivers/vector_user.c +++ b/arch/um/drivers/vector_user.c @@ -141,7 +141,7 @@ static int create_tap_fd(char *iface) } memset(&ifr, 0, sizeof(ifr)); ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR; - strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1); + strscpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name)); err = ioctl(fd, TUNSETIFF, (void *) &ifr); if (err != 0) { @@ -171,7 +171,7 @@ static int create_raw_fd(char *iface, int flags, int proto) goto raw_fd_cleanup; } memset(&ifr, 0, sizeof(ifr)); - strncpy((char *)&ifr.ifr_name, iface, sizeof(ifr.ifr_name) - 1); + strscpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name)); if (ioctl(fd, SIOCGIFINDEX, (void *) &ifr) < 0) { err = -errno; goto raw_fd_cleanup;