Commit e30955d0 authored by Justin Stitt's avatar Justin Stitt Committed by Richard Weinberger
Browse files

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: default avatarJustin Stitt <justinstitt@google.com>
Acked-by: default avatarAnton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent 8f85f93b

arch/um/drivers/vector_user.c

+2 −2
Original line number Diff line number Diff line
@@ -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;